%0 journal article %@ 2373-9878 %A Baudis, S.,Roch, T.,Balk, M.,Wischke, C.,Lendlein, A.,Behl, M. %D 2024 %J ACS Biomaterials Science & Engineering %N 3 %P 1481–1493 %R doi:10.1021/acsbiomaterials.3c01803 %T Multivariate analysis of cellular uptake characteristics for a (co)polymer particle library %U https://doi.org/10.1021/acsbiomaterials.3c01803 3 %X Controlling cellular responses to nanoparticles so far is predominantly empirical, typically requiring multiple rounds of optimization of particulate carriers. In this study, a systematic model-assisted approach should lead to the identification of key parameters that account for particle properties and their cellular recognition. A copolymer particle library was synthesized by a combinatorial approach in soap free emulsion copolymerization of styrene and methyl methacrylate, leading to a broad compositional as well as constitutional spectrum. The proposed structure–property relationships could be elucidated by multivariate analysis of the obtained experimental data, including physicochemical characteristics such as molar composition, molecular weight, particle diameter, and particle charge as well as the cellular uptake pattern of nanoparticles. It was found that the main contributors for particle size were the polymers’ molecular weight and the zeta potential, while particle uptake is mainly directed by the particles’ composition. This knowledge and the reported model-assisted procedure to identify relevant parameters affecting particle engulfment of particulate carriers by nonphagocytic and phagocytic cells can be of high relevance for the rational design of pharmaceutical nanocarriers and assessment of biodistribution and nanotoxicity, respectively. %0 journal article %@ 1438-7492 %A Folikumah, M.Y.,Behl, M.,Lendlein, A.,Neffe, A.T. %D 2023 %J Macromolecular Materials and Engineering %N 11 %P 2300146 %R doi:10.1002/mame.202300146 %T A 4-Arm PEG-Thiodepsipeptide Precursor Enables Gelatinase-promoted Hydrogel Formation %U https://doi.org/10.1002/mame.202300146 11 %X In situ hydrogelation of injectable precursors upon biological stimulus is relevant to generate hydrogels under mild conditions and, potentially, at a biological side of interest. Here, it is shown that hydrolytic enzymes can be used to initiate the formation of covalent hydrogel networks, realizing a cleavage-leading-to-gelation strategy. For this purpose, a two-component system is used, consisting of a 4-arm polyethylene glycol-thiodepsipeptide conjugate, PEG4TDPo containing the matrix metalloproteinases MMP-2- and MMP-9-cleavable Ac-Pro-Leu-Gly#SLeu-Leu-Gly- thiodepsipeptide sequence releasing a thiol upon hydrolysis, and a maleimide functionalized 4-armed PEG (PEG4MAL). PEG4TDPo is synthesized in a PEG-functionalization protocol involving convergent and divergent synthetic steps without the need for rigorous purification procedures. In a fluorometric assay, it is shown that the construct is in fact cleaved by both investigated MMPs. PEG4TDPo in the presence of 10 wt.% PEG4MAL formed hydrogels upon addition of MMP-2 or -9 with average gelation times of 28 and 40 min, respectively, as is investigated by rheology. The much faster gelation times compared to the enzyme-free system showed the specific input of the enzymatic reactions. The MMP-assisted activation and crosslinking strategy can potentially become useful by targeting tissues showing an increased expression of MMPs, such as cancers, or to detect MMPs. %0 journal article %@ 2073-4360 %A Farhan, M.,Hartstein, D.S.,Pieper, Y.,Behl, M.,Lendlein, A.,Neffe, A.T. %D 2023 %J Polymers %N 9 %P 2233 %R doi:10.3390/polym15092233 %T Bio-inspired magnetically controlled reversibly actuating multimaterial fibers %U https://doi.org/10.3390/polym15092233 9 %X Movements in plants, such as the coiling of tendrils in climbing plants, have been studied as inspiration for coiling actuators in robotics. A promising approach to mimic this behavior is the use of multimaterial systems that show different elastic moduli. Here, we report on the development of magnetically controllable/triggerable multimaterial fibers (MMFs) as artificial tendrils, which can reversibly coil and uncoil on stimulation from an alternating magnetic field. These MMFs are based on deformed shape-memory fibers with poly[ethylene-co-(vinyl acetate)] (PEVA) as their core and a silicone-based soft elastomeric magnetic nanocomposite shell. The core fiber provides a temperature-dependent expansion/contraction that propagates the coiling of the MMF, while the shell enables inductive heating to actuate the movements in these MMFs. Composites with mNP weight content ≥ 15 wt% were required to achieve heating suitable to initiate movement. The MMFs coil upon application of the magnetic field, in which a degree of coiling N = 0.8 ± 0.2 was achieved. Cooling upon switching OFF the magnetic field reversed some of the coiling, giving a reversible change in coiling ∆n = 2 ± 0.5. These MMFs allow magnetically controlled remote and reversible actuation in artificial (soft) plant-like tendrils, and are envisioned as fiber actuators in future robotics applications. %0 journal article %@ 0935-9648 %A Farhan, M.,Klimm, F.,Thielen, M.,Rešetič, A.,Bastola, A.,Behl, M.,Speck, T.,Lendlein, A. %D 2023 %J Advanced Materials %N 2 %P 2211902,2211902 %R doi:10.1002/adma.202211902 %T Artificial tendrils mimicking plant movements by mismatching modulus and strain in core and shell %U https://doi.org/10.1002/adma.202211902 2 %X Motile organs have evolved in climbing plants enabling them to find a support and, after secure attachment, to reach for sunlight without investing in a self-supporting stem. Searching movements, the twining of stems, and the coiling of tendrils are involved in successful plant attachment. Such coiling movements have great potential in robotic applications, especially if they are reversible. Here, the underlying mechanism of tendril movement based on contractile fibers is reported, as illustrated by a function–morphological analysis of tendrils in several liana species and the encoding of such a principle in a core–shell multimaterial fiber (MMF) system. MMFs are composed of a shape-memory core fiber (SMCF) and an elastic shell. The shape-memory effect of the core fibers enables the implementation of strain mismatch in the MMF by physical means and provides thermally controlled reversible motion. The produced MMFs show coiling and/or uncoiling behavior, with a high reversible actuation magnitude of ≈400%, which is almost 20 times higher compared with similar stimuli for sensitive soft actuators. The movements in these MMFs rely on the crystallization/melting behavior of oriented macromolecules of SMCF. %0 journal article %@ 0264-1275 %A Wang, X.,Behl, M.,Lendlein, A.,Balk, M. %D 2023 %J Materials & Design %N %P 111511 %R doi:10.1016/j.matdes.2022.111511 %T Responses to single and multiple temperature-, medium-, and pH-stimuli triggering reversible shape shifts in hydrogel actuators %U https://doi.org/10.1016/j.matdes.2022.111511 %X Adaptivity is an essential capability of creatures to develop skills for surviving and reproducing. Mimicking such behavior would enable the design of biologically inspired functions. Hydrogel actuators are promising candidate materials capable of stimuli-responsive movements via water uptake and release. Here, for the first time, the adaptive-like movement of reprogrammable hydrogel actuators is demonstrated by integrating two independent functions: a temperature-triggered actuation and a medium- and pH-based modulated swelling, into one multiphase network. Reversible crystallization of poly(ε-caprolactone) (PCL) provided bending movements up to 71° (realized by temperature changes between 5 °C and 40 °C). Changing solvent from water to ethanol increased swellability up to 240 vol%. Bending angles decreased by 32° as some PCL fractions are dissolved in ethanol and cannot participate in the crystallization-induced elongation guiding the movement. When the actuators were modified with acrylic acid moieties, a modulated swelling between 270 vol% at pH = 13 and 130 vol% at pH = 1 was achieved. The resulting swelling/deswelling response induced reversible bending movements up to 54°. In consequence, the coupled functionalities (actuation and modulated swelling) resulted in conditioned actuation behavior as an intermediate feature between stimuli-sensitivity and adaptivity. %0 journal article %@ 2352-4928 %A Mazurek-Budzyńska, M.,Behl, M.,Neumann, R.,Lendlein, A. %D 2022 %J Materials Today Communications %N %P 102966 %R doi:10.1016/j.mtcomm.2021.102966 %T 4D-actuators by 3D-printing combined with water-based curing %U https://doi.org/10.1016/j.mtcomm.2021.102966 %X The shape and the actuation capability of state of the art robotic devices typically relies on multimaterial systems from a combination of geometry determining materials and actuation components. Here, we present multifunctional 4D-actuators processable by 3D-printing, in which the actuator functionality is integrated into the shaped body. The materials are based on crosslinked poly(carbonate-urea-urethane) networks (PCUU), synthesized in an integrated process, applying reactive extrusion and subsequent water-based curing. Actuation capability could be added to the PCUU, prepared from aliphatic oligocarbonate diol, isophorone diisocyanate (IPDI) and water, in a thermomechanical programming process. When programmed with a strain of εprog = 1400% the PCUU networks exhibited actuation apparent by reversible elongation ε'rev of up to 22%. In a gripper a reversible bending ε'rev(bend) in the range of 37–60% was achieved when the actuation temperature (Thigh) was varied between 45 °C and 49 °C. The integration of actuation and shape formation could be impressively demonstrated in two PCUU-based reversible fastening systems, which were able to hold weights of up to 1.1 kg. In this way, the multifunctional materials are interesting candidate materials for robotic applications where a freedom in shape design and actuation is required as well as for sustainable fastening systems. %0 conference lecture %@ %A Behl, M.,Tartivel, L.,You, Z.,Balk, M.,Blocki, A.,Lendlein, A. %D 2022 %J MRS Spring Meeting 2022 %N %P %T Sequential coupling of functions in hydrogels enables shape-memory hydrogels with pH; enzyme- or an inverse temperature sensitivity %U %X %0 conference lecture %@ %A Farhan, M.,Behl, M.,Kreatz, K.,Lendlein, A. %D 2022 %J MRS Spring Meeting 2022 %N %P %T Origami hand for soft robotics driven by thermally controlled polymeric fiber actuators %U %X %0 journal article %@ 1022-1336 %A Baudis, S.,Behl, M. %D 2022 %J Macromolecular Rapid Communications %N 12 %P 2100400 %R doi:10.1002/marc.202100400 %T High-Throughput and Combinatorial Approaches for the Development of Multifunctional Polymers %U https://doi.org/10.1002/marc.202100400 12 %X High-throughput (HT) development of new multifunctional polymers is accomplished by the combination of different HT tools established in polymer sciences in the last decade. Important advances are robotic/HT synthesis of polymer libraries, the HT characterization of polymers, and the application of spatially resolved polymer library formats, explicitly microarray and gradient libraries. HT polymer synthesis enables the generation of material libraries with combinatorial design motifs. Polymer composition, molecular weight, macromolecular architecture, etc. may be varied in a systematic, fine-graded manner to obtain libraries with high chemical diversity and sufficient compositional resolution as model systems for the screening of these materials for the functions aimed. HT characterization allows a fast assessment of complementary properties, which are employed to decipher quantitative structure–properties relationships. Moreover, these methods facilitate the HT determination of important surface parameters by spatially resolved characterization methods, including time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. Here current methods for the high-throughput robotic synthesis of multifunctional polymers as well as their characterization are presented and advantages as well as present limitations are discussed. %0 journal article %@ 2196-7350 %A Tartivel, L.,Blocki, A.,Braune, S.,Jung, F.,Behl, M.,Lendlein, A. %D 2022 %J Advanced Materials Interfaces %N 6 %P 2101588 %R doi:10.1002/admi.202101588 %T An Inverse Shape-Memory Hydrogel Scaffold Switching Upon Cooling in a Tissue-Tolerated Temperature Range %U https://doi.org/10.1002/admi.202101588 6 %X Tissue reconstruction has an unmet need for soft active scaffolds that enable gentle loading with regeneration-directing bioactive components by soaking up but also provide macroscopic dimensional stability. Here microporous hydrogels capable of an inverse shape-memory effect (iSME) are described, which in contrast to classical shape-memory polymers (SMPs) recover their permanent shape upon cooling. These hydrogels are designed as covalently photo cross-linked polymer networks with oligo(ethylene glycol)-oligo(propylene glycol)-oligo(ethylene glycol) (OEG-OPG-OEG) segments. When heated after deformation, the OEG-OPG-OEG segments form micelles fixing the temporary shape. Upon cooling, the micelles dissociate again, the deformation is reversed and the permanent shape is obtained. Applicability of this iSME is demonstrated by the gentle loading of platelet-rich plasma (PRP) without causing any platelet activation during this process. PRP is highly bioactive and is widely acknowledged for its regenerative effects. Hence, the microporous inverse shape-memory hydrogel (iSMH) with a cooling induced pore-size effect represents a promising candidate scaffold for tissue regeneration for potential usage in minimally invasive surgery applications. %0 journal article %@ 1742-5689 %A Bastola, A.,Soffiatti, P.,Behl, M.,Lendlein, A.,Rowe, N. %D 2021 %J Journal of the Royal Society Interface %N 178 %P 20210040 %R doi:10.1098/rsif.2021.0040 %T Structural performance of a climbing cactus: making the most of softness %U https://doi.org/10.1098/rsif.2021.0040 178 %X Climbing plants must reach supports and navigate gaps to colonize trees. This requires a structural organization ensuring the rigidity of so-called ‘searcher’ stems. Cacti have succulent stems adapted for water storage in dry habitats. We investigate how a climbing cactus Selenicereus setaceus develops its stem structure and succulent tissues for climbing. We applied a ‘wide scale’ approach combining field-based bending, tensile and swellability tests with fine-scale rheological, compression and anatomical analyses in laboratory conditions. Gap-spanning ‘searcher’ stems rely significantly on the soft cortex and outer skin of the stem for rigidity in bending (60–94%). A woody core contributes significantly to axial and radial compressive strength (80%). Rheological tests indicated that storage moduli were consistently higher than loss moduli indicating that the mucilaginous cortical tissue behaved like a viscoelastic solid with properties similar to physical or chemical hydrogels. Rheological and compression properties of the soft tissue changed from young to old stages. The hydrogel–skin composite is a multi-functional structure contributing to rigidity in searcher stems but also imparting compliance and benign failure in environmental situations when stems must fail. Soft tissue composites changing in function via changes in development and turgescence have a great potential for exploring candidate materials for technical applications. %0 journal article %@ 2159-6859 %A Folikumah, M.,Behl, M.,Lendlein, A. %D 2021 %J MRS Communications %N 4 %P 402-410 %R doi:10.1557/s43579-021-00041-z %T Reaction behaviour of peptide-based single thiol-thioesters exchange reaction substrate in the presence of externally added thiols %U https://doi.org/10.1557/s43579-021-00041-z 4 %X Identification of patterns in chemical reaction pathways aids in the effective design of molecules for specific applications. Here, we report on model reactions with a water-soluble single thiol-thioester exchange (TTE) reaction substrate, which was designed taking in view biological and medical applications. This substrate consists of the thio-depsipeptide, Ac-Pro-Leu-Gly-SLeu-Leu-Gly-NEtSH (TDP) and does not yield foul-smelling thiol exchange products when compared with aromatic thiol containing single TTE substrates. TDP generates an α,ω-dithiol crosslinker in situ in a ‘pseudo intramolecular’ TTE. Competitive intermolecular TTE of TDP with externally added “basic” thiols increased the crosslinker concentration whilst “acidic” thiols decreased its concentration. TDP could potentially enable in situ bioconjugation and crosslinking applications. %0 conference poster %@ %A Folikumah, M.,Behl, M.,Lendlein, A. %D 2021 %J Advanced Functional Polymers for Medicine (AFPM) %N %P %T Design and synthesis of 3-arm MMP-sensitive thio-depsipeptide hydrogel precursor %U %X %0 journal article %@ 2059-8521 %A Liang, X.,Behl, M.,Luetzow, K.,Lendlein, A. %D 2021 %J MRS Advances %N %P 764-768 %R doi:10.1557/s43580-021-00082-5 %T Cooligomers from morpholine-2,5-dione and para-dioxanone and catalyst complex SnOct2/2-hydroxyethyl sulfide %U https://doi.org/10.1557/s43580-021-00082-5 %X Complexes from catalysts and initiator can be used to insert a specific number of additional chemical functional groups in (co)polymers prepared by ring-opening polymerization (ROP) of lactones. We report on the synthesis of cooligomers from sec-butyl-morpholine-2,5-dione (SBMD) and para-dioxanone (PDX) by ROP with varied feed ratios in the bulk using the catalyst complex SnOct2/2-hydroxyethyl sulfide. Mn of the cooligomers (determined by GPC) decreased with decreasing SBMD feed ratio from 4200 ± 420 to 800 ± 80 g mol−1. When the feed ratio was reduced from 80 to 50 mol% the molar ratio of SBMD of the cooligomers (determined by 1H-NMR) remained nearly unchanged between 81 and 86 mol% and was attributed to a higher reactivity of SBMD. This assumption was confirmed by fractionation of GPC, in which an increase of SBMD with increasing molecular weight was observed. The catalyst/initiator system provides a high potential to create orthogonal building blocks by cleavage of the sulfide bond. %0 conference lecture %@ %A Liang, X.,Behl, M.,Lendlein, A. %D 2021 %J Virtual MRS Spring Meeting %N %P %T Teroligomers from Morpholine-2;5-Diones providing a large variety of repeating unit sequences %U %X %0 journal article %@ 2159-6859 %A Farhan, M.,Behl, M.,Kratz, K.,Lendlein, A. %D 2021 %J MRS Communications %N 4 %P 476-482 %R doi:10.1557/s43579-021-00058-4 %T Origami hand for soft robotics driven by thermally controlled polymeric fiber actuators %U https://doi.org/10.1557/s43579-021-00058-4 4 %X Active fibers can serve as artificial muscles in robotics or components of smart textiles. Here, we present an origami hand robot, where single fibers control the reversible movement of the fingers. A recovery/contracting force of 0.2 N with a work capacity of 0.175 kJ kg−1 was observed in crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, which could enable the bending movement of the fingers by contraction upon heating. The reversible opening of the fingers was attributed to a combination of elastic recovery force of the origami structure and crystallization-induced elongation of the fibers upon cooling. %0 journal article %@ 1525-7797 %A Folikumah, M.,Behl, M.,Lendlein, A. %D 2021 %J Biomacromolecules %N 5 %P 1875-1884 %R doi:10.1021/acs.biomac.0c01690 %T Thiol–Thioester Exchange Reactions in Precursors Enable pH-Triggered Hydrogel Formation %U https://doi.org/10.1021/acs.biomac.0c01690 5 %X Bio-interactive hydrogel formation in situ requires sensory capabilities toward physiologically relevant stimuli. Here, we report on pH-controlled in situ hydrogel formation relying on latent cross-linkers, which transform from pH sensors to reactive molecules. In particular, thiopeptolide/thio-depsipeptides were capable of pH-sensitive thiol–thioester exchange reactions to yield α,ω-dithiols, which react with maleimide-functionalized multi-arm polyethylene glycol to polymer networks. Their water solubility and diffusibility qualify thiol/thioester-containing peptide mimetics as sensory precursors to drive in situ localized hydrogel formation with potential applications in tissue regeneration such as treatment of inflamed tissues of the urinary tract. %0 journal article %@ 0264-1275 %A Bastola, A.,Rodriguez, N.,Behl, M.,Soffiatti, P.,Rowe, N.,Lendlein, A. %D 2021 %J Materials & Design %N %P 109515 %R doi:10.1016/j.matdes.2021.109515 %T Cactus-inspired design principles for soft robotics based on 3D printed hydrogel-elastomer systems %U https://doi.org/10.1016/j.matdes.2021.109515 %X Plants have evolved many capabilities to anchor, position their stems and leaves favourably, and adapt themselves to different environmental conditions by virtue of growing. Selenicereus setaceus is a cactus and is an impressive example of a climbing plant found mostly in the Atlantic forest formations of southern Brazil. This cactus displays striking changes in stem geometry along different stages of growth: older parts are circular while the younger parts are star-like in shape. Such a transformation in shape optimizes its flexural rigidity and allows the cactus to search in three-dimensionally complex environments. Its organisation offers novel schemes for the design of plant-inspired soft robotic systems. In this paper, we have created multi-material systems for soft robotics that display controlled movements as well as mimicking the cactus stem geometries from star-like to circular. The unique star-shaped geometry is 3D printed using a soft elastomer and hydrogel is used as an actuating component. Through anisotropic swelling, the hydrogel-elastomer system adjusts its configuration and shows a controlled movement. Furthermore, the isotropic swelling of the hydrogel of the artificial cactus multi-material system result in the change in shape from star-like to circular as the cactus does naturally in the tropical forest. %0 journal article %@ 2059-8521 %A Rodriguez, N.,Bastola, A.,Behl, M.,Soffiatti, P.,Rowe, N.,Lendlein, A. %D 2021 %J MRS Advances %N 25 %P 625-630 %R doi:10.1557/s43580-021-00081-6 %T Approaches of combining a 3D-printed elastic structure and a hydrogel to create models for plant-inspired actuators %U https://doi.org/10.1557/s43580-021-00081-6 25 %X Inspired by the interesting functional traits of a climbing cactus, Selenicereus setaceus, found in the forest formations of Southeastern Brazil, we formulated a hypothesis that we can directly learn from the plants to develop multi-functional artificial systems by means of a multi-disciplinary approach. In this context, our approach is to take advantage of 3D-printing techniques and shape-memory hydrogels synergistically to mimic the functional traits of the cactus. This work reports on the preliminary investigation of cactus-inspired artificial systems. First, we 3D-printed soft polymeric materials and characterized them, which defines the structure and is a passive component of a multi-material system. Second, different hydrogels were synthesized and characterized, which is an active component of a multi-material system. Finally, we investigated how the hydrogel can be integrated into the 3D-printed constructs to develop artificial functional systems. %0 conference lecture %@ %A Bastola, A.,Behl, M.,Soffiatti, P.,Rowe, N.,Lendlein, A. %D 2021 %J Virtual MRS Spring Meeting 2021 %N %P %T Evolutionary Design of Cactus-inspired Soft Robotics Based on 3D-printed Multimaterial Construct %U %X %0 journal article %@ 1422-0067 %A Neffe, A.,Löwenberg, C.,Julich-Gruner, K.,Behl, M.,Lendlein, A. %D 2021 %J International Journal of Molecular Sciences %N 11 %P 5892 %R doi:10.3390/ijms22115892 %T Thermally-Induced Shape-Memory Behavior of Degradable Gelatin-Based Networks %U https://doi.org/10.3390/ijms22115892 11 %X Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) α,ω-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27–23 kPa and Young’s moduli of 215–360 kPa at 4 °C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 °C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates Rr close to 100% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix. %0 journal article %@ 1944-8244 %A Balk, M.,Behl, M.,Nöchel, U.,Lendlein, A. %D 2021 %J ACS Applied Materials and Interfaces %N 7 %P 8095-8101 %R doi:10.1021/acsami.1c00466 %T Enzymatically Triggered Jack-in-the-Box-like Hydrogels %U https://doi.org/10.1021/acsami.1c00466 7 %X Enzymes can support the synthesis or degradation of biomacromolecules in natural processes. Here, we demonstrate that enzymes can induce a macroscopic-directed movement of microstructured hydrogels following a mechanism that we call a “Jack-in-the-box” effect. The material’s design is based on the formation of internal stresses induced by a deformation load on an architectured microscale, which are kinetically frozen by the generation of polyester locking domains, similar to a Jack-in-the-box toy (i.e., a compressed spring stabilized by a closed box lid). To induce the controlled macroscopic movement, the locking domains are equipped with enzyme-specific cleavable bonds (i.e., a box with a lock and key system). As a result of enzymatic reaction, a transformed shape is achieved by the release of internal stresses. There is an increase in entropy in combination with a swelling-supported stretching of polymer chains within the microarchitectured hydrogel (i.e., the encased clown pops-up with a pre-stressed movement when the box is unlocked). This utilization of an enzyme as a physiological stimulus may offer new approaches to create interactive and enzyme-specific materials for different applications such as an optical indicator of the enzyme’s presence or actuators and sensors in biotechnology and in fermentation processes. %0 conference lecture %@ %A Farhan, M.,Rešetič, A.,Bastola, A.,Behl, M.,Lendlein, A. %D 2021 %J 2021 Virtual MRS Spring Meeting %N %P %T Artificial tendrils mimicking plant movements by mismatching modulus and length in multimaterial polymeric systems %U %X %0 journal article %@ 0014-3057 %A Behl, M.,Balk, M.,Lützow, K.,Lendlein, A. %D 2021 %J European Polymer Journal %N %P 110207 %R doi:10.1016/j.eurpolymj.2020.110207 %T Impact of block sequence on the phase morphology of multiblock copolymers obtained by high-throughput robotic synthesis %U https://doi.org/10.1016/j.eurpolymj.2020.110207 %X The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non-miscible block types. We hypothesized that a strictly alternating sequence should favour phase segregation and in this way the elastic properties. A library of well-defined MBCs composed of two different hydrophobic, semi-crystalline blocks providing domains with well-separated melting temperatures (Tms) were synthesized from the same type of precursor building blocks as strictly alternating (MBCsalt) or random (MBCsran) MBCs and compared. Three different series of MBCsalt or MBCsran were synthesized by high-throughput synthesis by coupling oligo(ε-caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification in which the molar ratio of the reaction partners was slightly adjusted. Maximum of weight average molecular weight (Mw) were 65,000 g∙mol−1, 165,000 g∙mol−1, and 168,000 g∙mol−1 for MBCsalt and 80,500 g∙mol−1, 100,000 g∙mol−1, and 147,600 g∙mol−1 for MBCsran. When Mw increased, a decrease of both Tms associated to the melting of the OCL and OTHF domains was observed for all MBCs. Tm (OTHF) of MBCsran was always higher than Tm (OTHF) of MBCsalt, which was attributed to a better phase segregation. In addition, the elongation at break of MBCsalt was almost half as high when compared to MBCsran. In this way this study elucidates role of the block length and sequence structure in MBCs and enables a quantitative discussion of the structure-function relationship when two semi-crystalline block segments are utilized for the design of block copolymers. %0 journal article %@ 1022-1352 %A Zhang, P.,Rešetic, A.,Behl, M.,Lendlein, A. %D 2021 %J Macromolecular Chemistry and Physics %N 3 %P 2000394 %R doi:10.1002/macp.202000394 %T Multifunctionality in Polymer Networks by Dynamic of Coordination Bonds %U https://doi.org/10.1002/macp.202000394 3 %X The need for multifunctional materials is driven by emerging technologies and innovations, such as in the field of soft robotics and tactile or haptic systems, where minimizing the number of operational components is not only desirable, but can also be essential for realizing such devices. This study report on designing a multifunctional soft polymer material that can address a number of operating requirements such as solvent resistance, reshaping ability, self‐healing capability, fluorescence stimuli‐responsivity, and anisotropic structural functions. The numerous functional abilities are associated to rhodium(I)–phosphine coordination bonds, which in a polymer network act with their dynamic and non‐covalently bonded nature as multifunctional crosslinks. Reversible aggregation of coordination bonds leads to changes in fluorescence emission intensity that responds to chemical or mechanical stimuli. The fast dynamics and diffusion of rhodium–phosphine ions across and through contacting areas of the material provide for reshaping and self‐healing abilities that can be further exploited for assembly of multiple pieces into complex forms, all without any loss to material‐sensing capabilities. %0 journal article %@ 0014-3057 %A Liang, X.,Behl, M.,Lendlein, A. %D 2021 %J European Polymer Journal %N %P 110189 %R doi:10.1016/j.eurpolymj.2020.110189 %T Dihydroxy terminated teroligomers from morpholine-2,5-diones %U https://doi.org/10.1016/j.eurpolymj.2020.110189 %X Oligodepsipeptides (ODPs) attract increasing attention as degradable materials in controlled drug delivery or as building blocks for nano-carriers. Their strong intermolecular interactions provide high stability. Tailoring the side groups of the amino acid repeating units to achieve a strong affinity to particular drugs allows a high drug-loading capacity. Here we describe synthesis and characterization of dihydroxy terminated teroligodepsipeptides (ter-ODPs) by ring-opening copolymerization (ROP) of three different morpholine-2,5-diones (MDs) in bulk in order to provide a set of teroligomers with structural variation for drug release or transfection. Ter-ODPs with equivalent co-monomer feed ratios were prepared as well as ter-ODPs, in which the co-monomer feed ratio was varied between 9 mol% and 78 mol%. Ter-ODPs were synthesized by ROP using 1,1,10,10-tetra-n-butyl-1,10-distanna-2,9,11,18-tetraoxa-5,6,14,15-tetrasulfur-cyclodecane (tin(IV) alkoxide) that was obtained by the reaction of dibutyl tin(II) oxide with 2-hydroxyethyl disulfide. The number average molecular weight (Mn) of ter-ODPs, determined by 1H NMR and gel permeation chromatography (GPC), ranged between 4000 g·mol−1 and 8600 g·mol−1. Co-monomer compositions in ter-ODPs could be controlled by changing the feed ratio of co-monomers as observed by 1H NMR spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The amount of remaining monomers as determined by 1H NMR could be kept below 1 wt%. Macrocycles as main sources of byproducts as determined from MALDI-TOF-MS measurements were significantly lower as compared to polymerization by Sn(Oct)2. Glass-transition temperature (Tg) of ter-ODPs ranged between 59 °C and 70 °C. %0 journal article %@ 1438-7492 %A Behl, M.,Balk, M.,Mansfeld, U.,Lendlein, A. %D 2021 %J Macromolecular Materials and Engineering %N 3 %P 2000672 %R doi:10.1002/mame.202000672 %T Phase Morphology of Multiblock Copolymers Differing in Sequence of Blocks %U https://doi.org/10.1002/mame.202000672 3 %X The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non‐miscible block types. It is hypothesized that a strictly alternating sequence should impact phase segregation. A library of well‐defined MBC obtained by coupling oligo(ε‐caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification results in strictly alternating (MBCalt) or random (MBCran) MBC. The three different series has a weight average molecular weight (Mw) of 65 000, 165 000, and 168 000 g mol−1 for MBCalt and 80 500, 100 000, and 147 600 g mol−1 for MBCran. When the chain length of OCL building blocks is increased, the tendency for phase segregation is facilitated, which is attributed to the decrease in chain mobility within the MBC. Furthermore, it is found that the phase segregation disturbs the crystallization by causing heterogeneities in the semi‐crystalline alignment, which is attributed to an increase of the disorder of the OCL semi‐crystalline alignment. %0 journal article %@ 1438-7492 %A Farhan, M.,Chaudhary, D.,Nöchel, U.,Behl, K.,Kratz, K.,Lendlein, A. %D 2021 %J Macromolecular Materials and Engineering %N 2 %P 2000579 %R doi:10.1002/mame.202000579 %T Electrical Actuation of Coated and Composite Fibers Based on Poly[ethylene‐co‐(vinyl acetate)] %U https://doi.org/10.1002/mame.202000579 2 %X Robots are typically controlled by electrical signals. Resistive heating is an option to electrically trigger actuation in thermosensitive polymer systems. In this study electrically triggerable poly[ethylene‐co‐(vinyl acetate)] (PEVA)‐based fiber actuators are realized as composite fibers as well as polymer fibers with conductive coatings. In the coated fibers, the core consists of crosslinked PEVA (cPEVA), while the conductive coating shell is achieved via a dip coating procedure with a coating thickness between 10 and 140 µm. The conductivity of coated fibers σ = 300–550 S m−1 is much higher than that of the composite fibers σ = 5.5 S m−1. A voltage (U) of 110 V is required to heat 30 cm of coated fiber to a targeted temperature of ≈ 65 °C for switching in less than a minute. Cyclic electrical actuation investigations reveal ε′rev = 5 ± 1% reversible change in length for coated fibers. The fabrication of such electro‐conductive polymeric actuators is suitable for upscaling so that their application potential as artificial muscles can be explored in future studies. %0 conference lecture %@ %A Gossen, M.,Lau, S.,Moradian, H.,Behl, M.,Lendlein, A. %D 2021 %J 2nd Joint Meeting of The European Society for Clinical Hemorheology and Microcirculation; The International Society for Clinical Hemorheology; and The International Society of Biorheology (ESCHM-ISCHM-ISB) %N %P %T Nanoparticle-mediated delivery of nucleic acids in primary human endothelial cells %U %X %0 conference poster %@ %A Folikumah, M.,Behl, M.,Lendlein, A. %D 2021 %J 2021 Virtual MRS Spring Meeting %N %P %T A peptide based latent crosslinker activated by thiol-thioester exchange reaction %U %X %0 conference lecture (invited) %@ %A Behl, M.,Lendlein, A. %D 2021 %J Living Machines 2021; The International Conference on Biomimentic and Biohybrid Systems %N %P %T Bio-inspired polymer-based actuators for soft robots %U %X %0 journal article %@ 0884-2914 %A Behl, M.,Zhao, Q.,Lendlein, A. %D 2020 %J Journal of Materials Research %N 18 %P 2396-2404 %R doi:10.1557/jmr.2020.204 %T Glucose-responsive shape-memory cryogels %U https://doi.org/10.1557/jmr.2020.204 18 %X Boronic ester bonds can be reversibly formed between phenylboronic acid (PBA) and triol moieties. Here, we aim at a glucose-induced shape-memory effect by implementing such bonds as temporary netpoints, which are cleavable by glucose and by minimizing the volume change upon stimulation by a porous cryogel structure. The polymer system consisted of a semi-interpenetrating network (semi-IPN) architecture, in which the triol moieties were part of the permanent network and the PBA moieties were located in the linear polymer diffused into the semi-IPN. In an alkaline medium (pH = 10), the swelling ratio was approximately 35, independent of Cglu varied between 0 and 300 mg/dL. In bending experiments, shape fixity Rf ≈ 80% and shape recovery Rr ≈ 100% from five programming/recovery cycles could be determined. Rr was a function of Cglu in the range from 0 to 300 mg/dL, which accords with the fluctuation range of Cglu in human blood. In this way, the shape-memory hydrogels could play a role in future diabetes treatment options. %0 journal article %@ 2059-8521 %A Behl, M.,Razzaq, M.,Mazurek-Budzyñska, M.,Lendlein, A. %D 2020 %J MRS Advances %N 45 %P 2317-2330 %R doi:10.1557/adv.2020.345 %T Polyetheresterurethane Based Porous Scaffolds with Tailorable Architectures by Supercritical CO2 Foaming %U https://doi.org/10.1557/adv.2020.345 45 %X Porous three-dimensional (3D) scaffolds are promising treatment options in regenerative medicine. Supercritical and dense-phase fluid technologies provide an attractive alternative to solvent-based scaffold fabrication methods. In this work, we report on the fabrication of poly-etheresterurethane (PPDO-PCL) based porous scaffolds with tailorable pore size, porosity, and pore interconnectivity by using supercritical CO2 (scCO2) fluid-foaming. The influence of the processing parameters such as soaking time, soaking temperature and depressurization on porosity, pore size, and interconnectivity of the foams were investigated. The average pore diameter could be varied between 100–800 μm along with a porosity in the range from (19 ± 3 to 61 ± 6)% and interconnectivity of up to 82%. To demonstrate their applicability as scaffold materials, selected foams were sterilized via ethylene oxide sterilization. They showed negligible cytotoxicity in tests according to DIN EN ISO 10993-5 and 10993-12 using L929 cells. The study demonstrated that the pore size, porosity and the interconnectivity of this multi-phase semicrystalline polymer could be tailored by careful control of the processing parameters during the scCO2 foaming process. In this way, PPDO-PCL scaffolds with high porosity and interconnectivity are potential candidate materials for regenerative treatment options. %0 journal article %@ 1525-7797 %A You, Z.,Behl, M.,Grage, S.,Bürck, J.,Zhao, Q.,Ulrich, A.,Lendlein, A. %D 2020 %J Biomacromolecules %N 2 %P 680-687 %R doi:10.1021/acs.biomac.9b01390 %T Shape-Memory Effect by Sequential Coupling of Functions over Different Length Scales in an Architectured Hydrogel %U https://doi.org/10.1021/acs.biomac.9b01390 2 %X The integration of functions in materials in order to gain macroscopic effects in response to environmental changes is an ongoing challenge in material science. Here, functions on different hierarchical levels are sequentially linked to translate a pH-triggered conformational transition from the molecular to the macroscopic level to induce directed movements in hydrogels. When the pH is increased, lysine-rich peptide molecules change their conformation into a β-hairpin structure because of the reduced electrostatic repulsion among the deprotonated amino groups. Coupled to this conformation change is the capability of the β-hairpin motifs to subsequently assemble into aggregates acting as reversible cross-links, which are used as controlling units to fix a temporary macroscopic shape. A structural function implemented into the hydrogel by a microporous architecture-enabled nondisruptive deformation upon compression by buckling of pore walls and their elastic recovery. Coupled to this structural function is the capability of the porous material to enhance the diffusion of ions into the hydrogel and to keep the dimension of the macroscopic systems almost constant when the additional cross-links are formed or cleaved as it limits the dimensional change of the pore walls. Covalent cross-linking of the hydrogel into a polymer network acted as gear shift to ensure translation of the function on the molecular level to the macroscopic dimension. In this way, the information of a directed shape-shift can be programmed into the material by mechanical deformation and pH-dependent formation of temporary net points. The information could be read out by lowering the pH. The peptides reverted back into their original random coil conformation and the porous polymer network could recover from the previously applied elastic deformation. The level of multifunctionality of the hydrogels can be increased by implementation of additional orthogonal functions such as antimicrobicity by proper selection of multifunctional peptides, which could enable sophisticated biomedical devices. %0 conference lecture %@ %A Behl, M.,Balk, M.,Mansfeld, U.,Lendlein, A. %D 2020 %J Virtual MRS Spring/Fall Meeting 2020 %N %P %T Robot-Assisted Synthesis of Alternating and Random Multiblock Copolymers Based on Oligo(ε-caprolactone)/Oligotetrahydrofurane and Their Phase Morphology %U %X %0 journal article %@ 2059-8521 %A Balk, M.,Behl, M.,Lendlein, A. %D 2020 %J MRS Advances %N 12 - 13 %P 655-666 %R doi:10.1557/adv.2019.447 %T Actuators Based on Oligo[(epsilon-caprolactone)-co-glycolide] with Accelerated Hydrolytic Degradation %U https://doi.org/10.1557/adv.2019.447 12 - 13 %X Polyester-based shape-memory polymer actuators are multifunctional materials providing reversible macroscopic shape shifts as well as hydrolytic degradability. Here, the function-function interdependencies (between shape shifts and degradation behaviour) will determine actuation performance and its life time.,In this work, glycolide units were incorporated in poly(ε-caprolactone) based actuator materials in order to achieve an accelerated hydrolytic degradation and to explore the function-function relationship. Three different oligo[(ε-caprolactone)-co-glycolide] copolymers (OCGs) with similar molecular weights (10.5 ± 0.5 kg∙mol−1) including a glycolide content of 8, 16, and 26 mol% (ratio 1:1:1 wt%) terminated with methacrylated moieties were crosslinked. The obtained actuators provided a broad melting transition in the range from 27 to 44 °C. The hydrolytic degradation of programmed OCG actuators (200% of elongation) resulted in a reduction of sample mass to 51 wt% within 21 days at pH = 7.4 and 40 °C. Degradation results in a decrease of Tm associated to the actuating units and increasing Tm associated to the skeleton forming units. The actuation capability decreased almost linear as function of time. After 11 days of hydrolytic degradation the shape-memory functionality was lost. Accordingly, a fast degradation behaviour as required, e.g., for actuator materials intended as implant material can be realized. %0 conference lecture %@ %A Behl, M.,Zhao, Q.,Lendlein, A. %D 2020 %J Virtual MRS Spring/Fall Meeting 2020 %N %P %T Glucose-responsive shape-memory cryogels %U %X %0 journal article %@ 1022-1336 %A Zhang, P.,Behl, M.,Balk, M.,Peng, X.,Lendlein, A. %D 2020 %J Macromolecular Rapid Communications %N 7 %P 1900658 %R doi:10.1002/marc.201900658 %T Shape‐Programmable Architectured Hydrogels Sensitive to Ultrasound %U https://doi.org/10.1002/marc.201900658 7 %X On‐demand motion of highly swollen polymer systems can be triggered by changes in pH, ion concentrations, or by heat. Here, shape‐programmable, architectured hydrogels are introduced, which respond to ultrasonic‐cavitation‐based mechanical forces (CMF) by directed macroscopic movements. The concept is the implementation and sequential coupling of multiple functions (swellability in water, sensitivity to ultrasound, shape programmability, and shape‐memory) in a semi‐interpenetrating polymer network (s‐IPN). The semi‐IPN‐based hydrogels are designed to function through rhodium coordination (Rh‐s‐IPNH). These coordination bonds act as temporary crosslinks. The porous hydrogels with coordination bonds (degree of swelling from 300 ± 10 to 680 ± 60) exhibit tensile strength σmax up to 250 ± 60 kPa. Shape fixity ratios up to 90% and shape recovery ratios up to 94% are reached. Potential applications are switches or mechanosensors. %0 journal article %@ 0266-3538 %A Wong, T.,Behl, M.,Yusoff, N.,Li, T.,Wahit, M.,Ismail, A.,Zhao, Q.,Lendlein, A. %D 2020 %J Composites Science and Technology %N %P 108138 %R doi:10.1016/j.compscitech.2020.108138 %T Bio-based composites from plant based precursors and hydroxyapatite with shape-memory capability %U https://doi.org/10.1016/j.compscitech.2020.108138 %X A series of bio-based composites consisting of degradable thermoset poly[xylitol-(1,12-dodecanedioate)] (PXD) and hydroxyapatite microparticles (HA) was prepared. Equimolar amounts of xylitol and 1,12-dodecanedioic acid were reacted under catalyst-free polyesterification and the synthesized composites (PXDHCy) consist HA particles ranging between 0 wt% and 20 wt%. Crystallinity of the polymer matrix decreased at low content of HA (5 wt%) as the microparticles hindered crystallization of 1,12-dodecanedioate segment and then increased when the content of HA was raised (from 10 wt% to 20 wt%) as the polymer chains crystallized on surface of microparticles. All PXD and PXDHCy are able to hydrolytically degrade with around 7 wt% to 20 wt% mass loss after 16 weeks incubation in water (rate depends on HA content). The capability of PXD and PXDHCy composites to keep a temporary shape after a deformation process correlated with the polymer crystallinity whereas the shape recovery was 99%. The switching temperatures of PXD and PXDHCy composites ranged around 50 °C (and correlated to the melting-transition temperature) and did not vary with the loading of HA. A prototype of PXDHCy composite smart fixation plug was demonstrated and showed excellent potential to be used as bio-based fixation device for household appliances. %0 journal article %@ 1022-1336 %A Razzaq, M.,Behl, M.,Heuchel, M.,Lendlein, A. %D 2020 %J Macromolecular Rapid Communications %N 1 %P 1900440 %R doi:10.1002/marc.201900440 %T Matching Magnetic Heating and Thermal Actuation for Sequential Coupling in Hybrid Composites by Design %U https://doi.org/10.1002/marc.201900440 1 %X Sequentially coupling two material functions requires matching the output from the first with the input of the second function. Here, magnetic heating controls thermal actuation of a hybrid composite in a challenging system environment causing an elevated level of heat loss. The concept is a hierarchical design consisting of an inner actuator of nanocomposite material, which can be remotely heated by exposure to an alternating magnetic field (AMF) and outer layers of a porous composite system with a closed pore morphology. These porous layers act as heat insulators and as barriers to the surrounding water. By exposure to the AMF, a local bulk temperature of 71 °C enables the magnetic actuation of the device, while the temperature of the surrounding water is kept below 50 °C. Interestingly, the heat loss during magnetic heating leads to an increase of the water phase (small volume) temperature. The temperature increase is able to sequentially trigger an adjacent thermal actuator attached to the actuator composite. In this way it could be demonstrated how the AMF is able to initiate two kinds of independent actuations, which might be interesting for robotics operating in aqueous environments. %0 journal article %@ 1525-7797 %A Löwenberg, C.,Julich-Gruner, K.,Neffe, A.,Behl, M.,Lendlein, A. %D 2020 %J Biomacromolecules %N 6 %P 2024-2031 %R doi:10.1021/acs.biomac.9b01753 %T Salt-Induced Shape-Memory Effect in Gelatin-Based Hydrogels %U https://doi.org/10.1021/acs.biomac.9b01753 6 %X Hydrophilic biopolymers display a strong tendency for self-organization into stable secondary, tertiary, and quaternary structures in aqueous environments. These structures are sensitive to changes in external conditions, such as temperature, pH or ions/salts, which may lead to molecular and/or macroscopic transitions. Here, we report on biopolymer-based stimuli-sensitive switchable matrices showing a shape-memory function as an output being alternatively switched by two different input signals, such as environmental changes in salt concentration or temperature. This was realized by implementing a shape-memory function in hydrogels based on the coil-to-helix transition of protein chains in gelatin-based networks. The hydrogels exhibited mechanical properties similar to that of soft tissue (storage modulus G′ = 1–100 kPa) and high swelling capabilities (Q = 1000–3000 vol %). In these gelatin-based networks, the covalent netpoints defined the permanent shape while after deformation helicalization of the gelatin acted as reversible stimuli-sensitive switches providing additional crosslinks capable of fixing the deformed temporary shape. By using either chaotropic salts to suppress gelatin helicalization or kosmotropic salts to support conformational changes of gelatin toward a helical orientation, these additional crosslinks could be cleaved or formed. In bending experiments, the strain fixity (Rf) and strain recovery ratios (Rr) were determined. While Rf ranged from 65 to 95% and was depending on the network composition, Rr were independent of the hydrogel composition with values about 100%. In addition, Rf and Rr were independent of the type of chaotropic salt that was used in this study, showing equal Rf and Rr values for MgCl2, NaSCN, and Mg(SCN)2. %0 journal article %@ 2059-8521 %A Folikumah, M.,Neffe, A.,Behl, M.,Lendlein, A. %D 2019 %J MRS Advances %N 46 - 47 %P 2515-2525 %R doi:10.1557/adv.2019.308 %T Thiol Michael-Type Reactions of Optically Active Mercapto-Acids in Aqueous Medium %U https://doi.org/10.1557/adv.2019.308 46 - 47 %X Defined chemical reactions in a physiological environment are a prerequisite for the in situ synthesis of implant materials potentially serving as matrix for drug delivery systems, tissue fillers or surgical glues. ‘Click’ reactions like thiol Michael-type reactions have been successfully employed as bioorthogonal reaction. However, due to the individual stereo-electronic and physical properties of specific substrates, an exact understanding their chemical reactivity is required if they are to be used for in-situ biomaterial synthesis. The chiral (S)-2-mercapto-carboxylic acid analogues of L-phenylalanine (SH-Phe) and L-leucine (SH-Leu) which are subunits of certain collagenase sensitive synthetic peptides, were explored for their potential for in-situ biomaterial formation via the thiol Michael-type reaction.,In model reactions were investigated the kinetics, the specificity and influence of stereochemistry of this reaction. We could show that only reactions involving SH-Leu yielded the expected thiol-Michael product. The inability of SH-Phe to react was attributed to the steric hindrance of the bulky phenyl group. In aqueous media, successful reaction using SH-Leu is thought to proceed via the sodium salt formed in-situ by the addition of NaOH solution, which was intented to aid the solubility of the mercapto-acid in water. Fast reaction rates and complete acrylate/maleimide conversion were only realized at pH 7.2 or higher suggesting the possible use of SH-Leu under physiological conditions for thiol Michael-type reactions. This method of in-situ formed alkali salts could be used as a fast approach to screen mercapto-acids for thio Michael-type reactions without the synthesis of their corresponding esters. %0 conference lecture %@ %A Balk, M.,Behl, M.,Lendlein, A. %D 2019 %J Arbeitskreis Innovative Technologien; Unternehmerverband Brandenburg e.V. %N %P %T Komplexe Bewegungen in Hydrogele %U %X %0 conference lecture %@ %A Balk, M.,Behl, M.,Lendlein, A. %D 2019 %J Polydays 2019 - Polymer Science and Engineering in View of Digitalization %N %P %T Hydrogels with quadruple-shape capability %U %X The increase in the number of shape shifts for temperature‐sensitive shape‐memory materials enabling,complex movements addresses a requirement from applications. Hydrogels are an interesting material,category according to their ability to enable diffusion processes through the material and their tissue‐like,mechanical properties. In contrast to non‐swollen systems, macroscopic movements in hydrogels are,limited by the applicable temperature range (phase transitions of water). So far, only two different shape,shifts could be implemented in hydrogels by means of two types of crystallizable side chains.,Here, we explored whether quadruple‐shape hydrogels enabling three shape transformations could be,created. A temperature independent swelling capacity in the hydrophilic polymer network is required to,ensure that directed movements are not related to swelling effects. Semi‐crystalline oligomeric side,chains were introduced in the hydrogel matrix by monomethacrylated oligo esters via radical,copolymerization. A demonstrator device was prepared using a casting mold fabrication by 3D printing,utilizing computer supported design. Polymer network forming components were copolymerized within,the mold, which was subsequently dissolved in water. The demonstrator object was obtained after,equilibrium swelling of the copolymer network in water. Three directed movements were successfully,realized when the temperature of the hydrogel system was increased from 5 °C to 90 °C resulting in an,overall recovery ratio related to the original shape above 90%. Accordingly, a quadruple‐shape effect,triggered by heat as stimulus as new record for complex movements in hydrogels was realized. For this,system, the applicable temperature range was limited by water as swelling media, distinctly separated,thermal transitions were necessary, and the overall elasticity indispensable for consecutive deformations,was reduced as result of partially chain segment orientation induced by swelling in water. Conclusively,,the challenges for more complex macroscopic shape shifts (e.g. penta‐ or hexa‐shape) hydrogels are,demanding for material systems providing higher elastic deformability and enabling distinct shape shifts,within narrow temperature ranges. %0 conference poster %@ %A Behl, M.,Peng, X.,Lützow, K.,Lendlein, A. %D 2019 %J Advanced Functional Polymers for Medicine 2019 %N %P %T Well-defined Telechelic Oliogodepsipeptides as Precursor Materials for Nanoparticulate Gene Carrier Systems %U %X Well-defined telechelic oligodepsipeptide oDPs,are the prerequisite to create the ABA,triblockcopolymers by sequential copolymer,synthesis. The most commonly used catalyst for,the polymerization of MDs as well as their copolymerization,with other cyclic monomers i.e.,dilactides and ε-caprolactone is tin(II)-2-,ethylhexanoate (Sn(Oct)2). An alternative,choice as catalyst for the ROP of lactone based,monomers is 1,1,6,6-tetra-n-butyl-1,6-distanna-,2,5,7,10-tetraoxacyclodecane (Sn(IV) alkoxide),,as demonstrated for the ROP of L-dilactide, 1,5-,dioxepan-2-one or ɛ-caprolactone. We hypothesized,that Sn(IV) alkoxide catalyzed ROP allows,a more precise control of the ROP reaction and,result in well-defined telechelic oDPs. %0 conference poster %@ %A Lützow, K.,Weigel, T.,Kosmella, H.,Behl, M.,Lendlein, A. %D 2019 %J AFPM - Advanced Functional Polymers for Medicine 2019 %N %P %T Shape Recovery of Polymeric Nanocomposite Foams by Direct and Inductive Heating %U %X %0 conference poster %@ %A Lützow, K.,Weigel, T.,Kosmella, H.,Behl, M.,Lendlein, A. %D 2019 %J Polydays 2019 - Polymer Science and Engineering in View of Digitalization %N %P %T Shape Recovery of Polymeric Nanocomposite Foams by Direct and Inductive Heating %U %X %0 journal article %@ 0897-4756 %A Zhang, P.,Behl, M.,Peng, X.,Balk, M.,Lendlein, A. %D 2019 %J Chemistry of Materials %N 15 %P 5402-5407 %R doi:10.1021/acs.chemmater.9b00363 %T Chemoresponsive Shape-Memory Effect of Rhodium–Phosphine Coordination Polymer Networks %U https://doi.org/10.1021/acs.chemmater.9b00363 15 %X Chemoresponsive polymers are of technological significance for smart sensors or systems capable of molecular recognition. An important key requirement for these applications is the material’s structural integrity after stimulation. We explored whether covalently cross-linked metal ion–phosphine coordination polymers (MPN) can be shaped into any temporary shape and are capable of recovering from this upon chemoresponsive exposure to triphenylphosphine (Ph3P) ligands, whereas the MPN provide structural integrity. Depending on the metal-ion concentration used during synthesis of the MPN, the degree of swelling of the coordination polymer networks could be adjusted. Once the MPN was immersed into Ph3P solution, the reversible ligand-exchange reaction between the metal ions and the free Ph3P in solution causes a decrease of the coordination cross-link density in MPN again. The Ph3P-treated MPN was able to maintain its original shape, indicating a certain stability of shape even after stimulation. In this way, chemoresponsive control of the elastic properties (increase in volume and decrease of mechanical strength) of the MPN was demonstrated. This remarkable behavior motivated us to explore whether the MPN are capable of a chemoresponsive shape-memory effect. In initial experiments, shape fixity of around 60% and shape recovery of almost 90% were achieved when the MPN was exposed to Ph3P in case of rhodium. Potential applications for chemoresponsive shape-memory systems could be shapable semiconductors, e.g., for lighting or catalysts, which provide catalytic activity on demand. %0 conference poster %@ %A Folikumah, M.,Neffe, A.,Behl, M.,Lendlein, A. %D 2019 %J Polydays 2019 - Polymer Science and Engineering in View of Digitalization %N %P %T Thiol-Michael reactions of optically active mercapto-acids in aqueous medium %U %X %0 book part %@ 2510-3458 %A Mazurek-Budzynska, M.,Razzaq, M.,Behl, M.,Lendlein, A. %D 2019 %J Functional Polymers. Polymers and Polymeric Composites %N %P 605-663 %R doi:10.1007/978-3-319-92067-2_18-1 %T Shape-Memory Polymers %U https://doi.org/10.1007/978-3-319-92067-2_18-1 %X Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of changing their shape on demand. A shape-memory function is a result of the polymer architecture together with the application of a specific programming procedure. Various possible mechanisms to induce the shape-memory effect (SME) can be realized, which can be based on thermal transitions of switching domains or on reversible molecular switches (e.g., supramolecular interactions, reversible covalent bonds). Netpoints, which connect the switching domains and determine the permanent shape, can be either provided by covalent bonds or by physical intermolecular interactions, such as hydrogen bonds or crystallites. This chapter reviews different ways of implementing the phenomenon of programmable changes in the polymer shape, including the one-way shape-memory effect (1-W SME), triple- and multi-shape effects (TSE/MSE), the temperature-memory effect (TME), and reversible shape-memory effects, which can be realized in constant stress conditions (rSME), or in stress-free conditions (reversible bidirectional shape-memory effect (rbSME)). Furthermore, magnetically actuated SMPs and shape-memory hydrogels (SMHs) are described to show the potential of the SMP technology in biomedical applications and multifunctional approaches. %0 journal article %@ 0141-3910 %A Mazurek-Budzynska, M.,Behl, M.,Razzaq, M.Y.,Noechel, U.,Rokicki, G.,Lendlein, A. %D 2019 %J Polymer Degradation and Stability %N %P 283-297 %R doi:10.1016/j.polymdegradstab.2019.01.032 %T Hydrolytic stability of aliphatic poly(carbonate-urea-urethane)s: Influence of hydrocarbon chain length in soft segment %U https://doi.org/10.1016/j.polymdegradstab.2019.01.032 %X Poly(carbonate-urethane)s (PCUs) exhibit improved resistance to hydrolytic degradation and in vivo stress cracking compared to poly(ester-urethane)s and their degradation leads to lower inflammation of the surrounding tissues. Therefore, PCUs are promising implant materials and are considered for devices such as artificial heart or spine implants. In this work, the hydrolytic stability of different poly(carbonate-urethane–urea)s (PCUUs) was studied under variation of the length of hydrocarbon chain (6, 9, 10, and 12 methylene units) between the carbonate linkages in the precursors. PCUUs were synthesized from isophorone diisocyanate and oligo(alkylene carbonate) diols using the moisture-cure method. The changes of sample weight, thermal and mechanical properties, morphology, as well as the degradation products after immersion in a buffer solution (PBS, pH = 7.4) for up to 10 weeks at 37 °C were monitored and analyzed. In addition, mechanical properties after 20 weeks (in PBS, 37 °C) were investigated. The gel content was determined based on swelling experiments in chloroform.,Based on the DSC analysis, slight increases of melting transitions of PCUUs were observed, which were attributed to structure reorganization related to annealing at 37 °C rather than to the degradation of the PCUU. Tensile strength after 20 weeks of all investigated samples remained in the range of 29–39 MPa, whereas the elongation at break εm decreased only slightly and remained in the range between 670 and 800%. Based on the characterization of degradation products after up to 10 weeks of immersion it was assessed that oligomers are mainly consisting of hard segments containing urea linkages, which could be assigned to hindered-urea dissociation mechanism. The investigations confirmed good resistance of PCUUs to hydrolysis. Only minor changes in the crystallinity, as well as thermal and mechanical properties were observed and depended on hydrocarbon chain length in soft segment of PCUUs. %0 journal article %@ 2059-8521 %A Balk, M.,Behl, M.,Lendlein, A. %D 2019 %J MRS Advances %N 21 %P 1193-1205 %R doi:10.1557/adv.2019.202 %T Hydrolytic Degradation of Actuators Based on Copolymer Networks From Oligo(ε-caprolactone) Dimethacrylate and n-Butyl Acrylate %U https://doi.org/10.1557/adv.2019.202 21 %X Shape-memory polymer actuators often contain crystallizable polyester segments. Here, the influence of accelerated hydrolytic degradation on the actuation performance in copolymer networks based on oligo(ε-caprolactone) dimethacrylate (OCL) and n-butyl acrylate is studied. The semi-crystalline OCL was utilized as crosslinker with molecular weights of 2.3 and 15.2 kg∙mol−1 (ratio: 1:1 wt%) and n-butyl acrylate (25 wt% relative to OCL content) acted as softening agent creating the polymer main chain segments within the network architecture. The copolymer networks were programmed by 50% elongation and were degraded by means of alkaline hydrolysis utilizing sodium hydroxide solution (pH = 13). Experiments were performed in the range of the broad melting range of the actuators at 40 °C. The degradation of test specimen was monitored by the sample mass, which was reduced by 25 wt% within 105 d. As degradation products, fragments of OCL with molecular masses ranging from 400 to 50.000 g·mol-1 could be detected by NMR spectroscopy and GPC measurements. The cleavage of ester groups included in OCL segments resulted in a decrease of the melting temperature (Tm) related to the actuator domains (amorphous at the temperature of degradation) and simultaneously, the Tm associated to the skeleton domain was increased (semi-crystalline at the temperature of degradation).,The alkaline hydrolysis decreased the polymer chain orientation of OCL domains until a random alignment of crystalline domains was obtained. This result was confirmed by cyclic thermomechanical actuation tests. The performance of directed movements decreased almost linearly as function of degradation time resulting in the loss of functionality when the orientation of polymer chains disappeared. Here, actuators were able to provide reversible movements until 91 d when the accelerated bulk degradation procedure using alkaline hydrolysis (pH = 13) was applied. Accordingly, a lifetime of more than one year can be guaranteed under physiological conditions (pH = 7.4) when, e.g., artificial muscles for biomimetic robots as potential application for these kind of shape-memory polymer actuators will be addressed. %0 conference poster %@ %A Folikumah, M.,Neffe, A.,Behl, M.,Lendlein, A. %D 2019 %J Advanced Functional Polymers for Medicine (AFPM) 2019 %N %P %T Thiol-Michael reactions of optically-active mercapto-acids in aqueous medium %U %X %0 journal article %@ 0964-1726 %A Zhang, Q.,Rudolph, T.,Benitez, A.J.,Gould, O.E.C.,Behl, M.,Kratz, K.,Lendlein, A. %D 2019 %J Smart Materials and Structures %N 5 %P 055037 %R doi:10.1088/1361-665X/ab10a1 %T Temperature-controlled reversible pore size change of electrospun fibrous shape-memory polymer actuator based meshes %U https://doi.org/10.1088/1361-665X/ab10a1 5 %X Fibrous membranes capable of dynamically responding to external stimuli are highly desirable in textiles and biomedical materials, where adaptive behavior is required to accommodate complex environmental changes. For example, the creation of fabrics with temperature-dependent moisture permeability or self-regulating membranes for air filtration is dependent on the development of materials that exhibit a reversible stimuli-responsive pore size change. Here, by imbuing covalently crosslinked poly(ε-caprolactone) (cPCL) fibrous meshes with a reversible bidirectional shape-memory polymer actuation (rbSMPA) we create a material capable of temperature-controlled changes in porosity. Cyclic thermomechanical testing was used to characterize the mechanical properties of the meshes, which were composed of randomly arranged microfibers with diameters of 2.3 ± 0.6 μm giving an average pore size of approx. 10 μm. When subjected to programming strains of ε m = 300% and 100% reversible strain changes of εʹrev = 22% ± 1% and 6% ± 1% were measured, with switching temperature ranges of 10 °C–30 °C and 45 °C–60 °C for heating and cooling, respectively. The rbSMPA of cPCL fibrous meshes generated a microscale reversible pore size change of 11% ± 3% (an average of 1.5 ± 0.6 μm), as measured by scanning electron microscopy. The incorporation of a two-way shape-memory actuation capability into fibrous meshes is anticipated to advance the development and application of smart membrane materials, creating commercially viable textiles and devices with enhanced performance and novel functionality. %0 journal article %@ 0964-1726 %A Balk, M.,Behl, M.,Lendlein, A. %D 2019 %J Smart Materials and Structures %N 5 %P 055026 %R doi:10.1088/1361-665X/ab0e91 %T Quadruple-shape hydrogels %U https://doi.org/10.1088/1361-665X/ab0e91 5 %X The capability of directed movements by two subsequent shape changes could be implemented in shape-memory hydrogels by incorporation of two types of crystallizable side chains. While in non-swollen polymer networks even more directed movements could be realized, the creation of multi-shape hydrogels is still a challenge. We hypothesize that a quadruple-shape effect in hydrogels can be realized, when a swelling capacity almost independent of temperature is generated, whereby directed movements could be enabled, which are not related to swelling. In this case, entropy elastic recovery could be realized by hydrophilic segments and the fixation of different macroscopic shapes by means of three semi-crystalline side chains generating temporary crosslinks. Monomethacrylated semi-crystalline oligomers were connected as side chains in a hydrophilic polymer network via radical copolymerization. Computer assisted modelling was utilized to design a demonstrator capable of complex shape shifts by creating a casting mold via 3D printing from polyvinyl alcohol. The demonstrator was obtained after copolymerization of polymer network forming components within the mold, which was subsequently dissolved in water. A thermally-induced quadruple-shape effect was realized after equilibrium swelling of the polymer network in water. Three directed movements were successfully obtained when the temperature was continuously increased from 5 °C to 90 °C with a recovery ratio of the original shape above 90%. Hence, a thermally-induced quadruple-shape effect as new record for hydrogels was realized. Here, the temperature range for the multi-shape effect was limited by water as swelling media (0 °C–100 °C), simultaneously distinctly separated thermal transitions were required, and the overall elasticity indispensable for successive deformations was reduced as result of partially chain segment orientation induced by swelling in water. Conclusively the challenges for penta- or hexa-shape gels are the design of systems enabling higher elastic deformability and covering a larger temperature range by switching to a different solvent. %0 journal article %@ 2059-8521 %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2019 %J MRS Advances %N 19 %P 1057-1065 %R doi:10.1557/adv.2019.123 %T Magneto-Mechanical Actuators with Reversible Stretching and Torsional Actuation Capabilities %U https://doi.org/10.1557/adv.2019.123 19 %X Composite actuators consisting of magnetic nanoparticles dispersed in a crystallizable multiphase polymer system can be remotely controlled by alternating magnetic fields (AMF). These actuators contain spatially segregated crystalline domains with chemically different compositions. Here, the crystalline domain associated to low melting transition range is responsible for actuation while the crystalline domain associated to the higher melting transition range determines the geometry of the shape change. This paper reports magneto-mechanical actuators which are based on a single crystalline domain of oligo(ω-pentadecalactone) (OPDL) along with covalently integrated iron(III) oxide nanoparticles (ioNPs). Different geometrical modes of actuation such as a reversible change in length or twisting were implemented by a magneto-mechanical programming procedure. For an individual actuation mode, the degree of actuation could be tailored by variation of the magnetic field strengths. This material design can be easily extended to other composites containing other magnetic nanoparticles, e.g. with a high magnetic susceptibility. %0 journal article %@ 1022-1336 %A Zhao, F.,Bonasera, A.,Noechel, U.,Behl, M.,Bleger, D. %D 2018 %J Macromolecular Rapid Communications %N 1 %P 1700527 %R doi:10.1002/marc.201700527 %T Reversible Modulation of Elasticity in Fluoroazobenzene-Containing Hydrogels Using Green and Blue Light %U https://doi.org/10.1002/marc.201700527 1 %X Hydrogels are soft materials that have found multiple applications in biomedicine and represent a good platform for the introduction of molecular switches and synthetic machines into macromolecular networks. Tuning their mechanical properties reversibly with light is appealing for a variety of advanced applications and has been demonstrated in the past; however, their activation typically requires the use of UV light, which displays several drawbacks related to its damaging character and limited penetration in tissues and materials. This study circumvents this limitation by introducing all‐visible ortho‐fluoroazobenzene switches into a hydrophilic network, which, as a result, can be activated with green or blue light. Photoisomerization of the photochromic moieties is accompanied by a reversible tuning of the elastic modulus. The translation of molecular isomerization within the network into macroscopic modulation of its mechanical properties is attributed to different aggregation tendencies of the E and Z isomers of the azobenzene derivatives. %0 conference poster %@ %A Noechel, U.,Behl, M.,Kratz, K.,Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %N %P %T Tailoring the Thermo-Mechanical Properties of Degradable Copolyetherester Urethanes Comprising Oligo(p-dioxanone) and Oligo(e-caprolactone) segments %U %X %0 conference poster %@ %A Balk, M.,Mazurek-Budzynska, M.,Behl, M.,Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %N %P %T Polycationic Particles Based on Polyethyleneimine and Poly(ethylene glycol) Functionalized Oligoester %U %X %0 journal article %@ 2059-8521 %A Yan, W.,Fang, L.,Noechel, U.,Gould, O.E.C.,Behl, M.,Kratz, K.,Lendlein, A. %D 2018 %J MRS Advances %N 63 %P 3741-3749 %R doi:10.1557/adv.2018.590 %T Investigating the Roles of Crystallizable and Glassy Switching Segments within Multiblock Copolymer Shape-Memory Materials %U https://doi.org/10.1557/adv.2018.590 63 %X The variation of the molecular architecture of multiblock copolymers has enabled the introduction of functional behaviour and the control of key mechanical properties. In the current study, we explore the synergistic relationship of two structural components in a shape-memory material formed of a multiblock copolymer with crystallizable poly(ε-caprolactone) and crystallizable poly[oligo(3S-iso-butylmorpholine-2,5-dione)] segments (PCL-PIBMD). The thermal and structural properties of PCL-PIBMD films were compared with PCL-PU and PIBMD-PU, investigated by means of DSC, SAXS and WAXS measurements. The shape-memory properties were quantified by cyclic, thermomechanical tensile tests, where deformation strains up to 900% were applied for programming PCL-PIBMD films at 50 °C. Toluene vapor treatment experiments demonstrated that the temporary shape was fixed mainly by glassy PIBMD domains at strains lower than 600%, with the PCL contribution to fixation increasing to 42±2% at programming strains of 900%. This study into the shape-memory mechanism of PCL-PIBMD provides insight into the structure-function relation in multiblock copolymers with both crystallizable and glassy switching segments. %0 conference lecture %@ %A Yan, W.,Fang, L.,Noechel, U.,Gould, O.E.C.,Behl, M.,Kratz, K.,Lendlein, A. %D 2018 %J 27th International Materials Research Congress %N %P %T Investigating the Roles of Crystallizable and Glassy Switching Segments within Multiblock Copolymer Shape-Memory Materials %U %X %0 conference lecture %@ %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2018 %J 27th International Materials Research Congress %N %P %T Thermally-Induced Actuation of Magnetic Nanocomposites Based on Oligo(Omega-Pentadecalactone) and Covalently Integrated Magnetic Nanoparticles %U %X %0 journal article %@ 2059-8521 %A Mazurek-Budzynska, M.,Balk, M.,Behl, M.,Lendlein, A. %D 2018 %J MRS Advances %N 50 %P 3033-3040 %R doi:10.1557/adv.2018.407 %T Polyethyleneimine and Poly(ethylene glycol) Functionalized Oligoester Based Polycationic Particles %U https://doi.org/10.1557/adv.2018.407 50 %X Polycationic particles based on a degradable oligoester core are interesting candidate materials for the transfection of polyanionic macromolecules like DNA, which would enable the degradation after delivery of condensed molecules. Good transfection efficiencies can be obtained when the size of the polyplex (containing both polycationic nanoparticles and polyanionic macromolecules) does not exceed 120 nm. Therefore, here we explored how size, but also dispersity, and surface charge of these carrier systems can be adjusted by variation of the block copolymer composition or the presence and ratio of a co-assembly agent. Polycationic particles were obtained based on an amphiphilic triblock copolymer from oligo[(ε-caprolactone)-co-glycolide] (CG) functionalized with polyethyleneimine (PEI) and diblock copolymer based on poly(ethylene glycol) (PEG) modified with CG. A second series of particles was created, in which the oligoester blocks contained only ε-caprolactone units, therefore the effect of the presence of glycolide units was also studied. In both series, the ratio between di- and triblock copolymers was systematically varied. Nano-sized particles ranging from 34.5 ± 0.2 nm to 97.9 ± 0.3 nm with controllable positive surface charges between 2.9 ± 0.2 mV and 18.1 ± 0.5 mV were obtained by self-assembly in PBS solution under intensive stirring. The incorporation of PEG-C diblock copolymers resulted in an increase of particle size, however no specific relation between composition, size, and polydispersity was observed. In case of PEG-CG diblock copolymers a rather systematic increase of the particles’ size with increasing content of diblock copolymer was shown. Furthermore, with a decrease of content of diblock copolymer in the particle structure zeta potential strongly increased. Additionally, the content of glycolide units in triblock copolymer increased the zeta potential of PEI-CG-PEI-based particles in comparison to PEI-C-PEI-based ones. Therefore, obtained particles could be used as potential target-oriented polycationic macromolecules for carrier systems. %0 journal article %@ 2059-8521 %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2018 %J MRS Advances %N 63 %P 3783-3791 %R doi:10.1557/adv.2018.613 %T Thermally-Induced Actuation of Magnetic Nanocomposites Based on Oligo(Omega-Pentadecalactone) and Covalently Integrated Magnetic Nanoparticles %U https://doi.org/10.1557/adv.2018.613 63 %X The incorporation of inorganic particles in a polymer matrix has been established as a method to adjust the mechanical performance of composite materials. We report on the influence of covalent integration of magnetic nanoparticles (MNP) on the actuation behavior and mechanical performance of hybrid nanocomposite (H-NC) based shape-memory polymer actuators (SMPA). The H-NC were synthesized by reacting two types of oligo(ω-pentadecalactone) (OPDL) based precursors with terminal hydroxy groups, a three arm OPDL (3AOPDL, Mn = 6000 g mol·1-1) and an OPDL (Mn =3300 g · mol-1) coated magnetite nanoparticle (Ø = 10 ± 2 nm), with a diisocyanate. These H-NC were compared to the homopolymer network regarding the actuation performance, contractual stress (σcontr) as well as thermal and mechanical properties. The melting range of the OPDL crystals (ΔTm,OPDL) was shifted in homo polymer networks from 36 °C – 76 °C to 41°C – 81 °C for H-NC with 9 wt% of MNP content. The actuators were explored by variation of separating temperature (Tsep), which splits the OPDL crystalline domain into actuating and geometry determining segments. Tsep was varied in the melting range of the nanocomposites and the actuation capability and contractual stress (σcontr) of the nanocomposite actuators could be adjusted. The reversible strain (εrev) was decreased from 11 ± 0.3% for homo polymer network to 3.2±0.3% for H-NC9 with 9 wt% of MNP indicating a restraining effect of the MNP on chain mobility. The results show that the performance of H-NCs in terms of thermal and elastic properties can be tailored by MNP content, however for higher reversible actuation, lower MNP contents are preferable. %0 lecture %@ %A Lendlein, A.,Schulz, B.,Schroeter, M.,Behl, M. %D 2018 %J %N %P %T Polymers in Medicine %U %X %0 conference lecture %@ %A Razzaq, M.,Behl, M.,Lendlein, A. %D 2018 %J XXVII International Materials Research Congress - IMRC 2018 %N %P %T Thermally-triggered actuators based on oligo(ω-pentadecalactone) hybrid nanocomposites %U %X %0 journal article %@ 2059-8521 %A Balk, M.,Lendlein, A.,Behl, M. %D 2018 %J MRS Advances %N 49 %P 2965-2973 %R doi:10.1557/adv.2018.319 %T High-Throughput Synthesis of Oligo(Epsilon-caprolactone) / Oligotetrahydrofuran Based Polyurethanes %U https://doi.org/10.1557/adv.2018.319 49 %X Robot assisted synthesis as part of high-throughput (HT) technology can assist in the creation of polymer libraries, e.g. polymers with a variety of molecular weights, by automatizing similar reactions. Especially for multiblock copolymers like polyurethanes (PUs) synthesized from telechels via polyaddition reaction, the adjustment of equivalent molar amounts of reactants requires a comprehensive investigation of end group functionality.,In this work, PUs based on oligo(ε-caprolactone) (OCL) / oligotetrahydrofuran (OTHF) as model components were designed utilizing HT synthesis enabling the quantitative determination of the optimized ratio between reactive end-groups via fully automated syntheses without major characterization effort of end group functionality. The semi-crystalline oligomeric telechelics were connected with a diisocyanate and OCL with a molecular weight of 2, 4, or 8 kg∙mol-1 was integrated. Here, optimized molecular weights between 90 ± 10 kg∙mol-1 (in case of OCL 8 kg∙mol-1) and 260 ± 30 kg∙mol-1 (in case of OCL 2 kg∙mol-1) were obtained with an isocyanate content of 120 mol%, whereby 100 mol% of isocyanate groups resulted only in molecular weights between 60 ± 6 kg∙mol-1 (OCL 8 kg∙mol-1) and 80 ± 10 kg∙mol-1 (OCL 2 kg∙mol-1). In addition to the optimized ratio between isocyanate and hydroxy end groups, quantitative influences of the OCL chain length and overall molecular weights of PUs on thermal and mechanical properties were detected. The melting temperatures (Tms) of OCL and OTHF domains were well separated for PUs of low molecular weight, the temperature interval between the Tms decreased when the molecular weight of the PUs was increased, and were even overlapping towards one broad Tm, when OCL 2 kg∙mol-1 was incorporated. The storage modulus E’ was highly dependent on OCL chain length exhibiting an increase with increasing molecular weight of OCL from 220 MPa to 440 MPa at 0 °C and decreased with increasing chain length of PUs. The elongation at break (εb) was analyzed below and above Tm of OTHF resulting in εb = 780-870% at 0 °C and εb = 510-830% at 30 °C for PUs of high molecular weight. Accordingly, stretchability of PUs was almost independent of the state of OTHF (semi crystalline or amorphous) but correlated with the OCL precursor chain length (increasing εb with increasing chain length) and overall molecular weight of PUs (PUs at higher molecular weight exhibited higher εb). Hence, the analysis of these quantitative influences between macromolecular structure of multiblock copolymers and the resulting properties (well separated Tms versus overlapping melting transition, improvement of stretchability) would enable the design of new tailored PUs. %0 journal article %@ 2051-6347 %A Wang, L.,Razzaq, M.Y.,Rudolph, T.,Heuchel, M.,Noechel, U.,Mansfeld, U.,Jiang, Y.,Gould, O.E.C.,Behl, M.,Kratz, K.,Lendlein, A. %D 2018 %J Materials Horizons %N 5 %P 861-867 %R doi:10.1039/C8MH00266E %T Reprogrammable, magnetically controlled polymeric nanocomposite actuators %U https://doi.org/10.1039/C8MH00266E 5 %X Soft robots and devices with the advanced capability to perform adaptive motions similar to that of human beings often have stimuli-sensitive polymeric materials as the key actuating component. The external signals triggering the smart polymers’ actuations can be transmitted either via a direct physical connection between actuator and controlling unit (tethered) or remotely without a connecting wire. However, the vast majority of such polymeric actuator materials are limited to one specific type of motion as their geometrical information is chemically fixed. Here, we present magnetically driven nanocomposite actuators, which can be reversibly reprogrammed to different actuation geometries by a solely physical procedure. Our approach is based on nanocomposite materials comprising spatially segregated crystallizable actuation and geometry determining units. Upon exposure to a specific magnetic field strength the actuators’ geometric memory is erased by the melting of the geometry determining units allowing the implementation of a new actuator shape. The actuation performance of the nanocomposites can be tuned and the technical significance was demonstrated in a multi-cyclic experiment with several hundreds of repetitive free-standing shape shifts without losing performance. %0 journal article %@ 0024-9297 %A Yan, W.,Rudolph, T.,Noechel, U.,Gould, O.,Behl, M.,Kratz, K.,Lendlein, A. %D 2018 %J Macromolecules %N 12 %P 4624-4632 %R doi:10.1021/acs.macromol.8b00322 %T Reversible Actuation of Thermoplastic Multiblock Copolymers with Overlapping Thermal Transitions of Crystalline and Glassy Domains %U https://doi.org/10.1021/acs.macromol.8b00322 12 %X Polymeric materials possessing specific features like programmability, high deformability, and easy processability are highly desirable for creating modern actuating systems. In this study, thermoplastic shape-memory polymer actuators obtained by combining crystallizable poly(ε-caprolactone) (PCL) and poly(3S-isobutylmorpholin-2,5-dione) (PIBMD) segments in multiblock copolymers are described. We designed these materials according to our hypothesis that the confinement of glassy PIBMD domains present at the upper actuation temperature contribute to the stability of the actuator skeleton, especially at large programming strains. The copolymers have a phase-segregated morphology, indicated by the well-separated melting and glass transition temperatures for PIBMD and PCL, but possess a partially overlapping Tm of PCL and Tg of PIBMD in the temperature interval from 40 to 60 °C. Crystalline PIBMD hard domains act as strong physical netpoints in the PIBMD−PCL bulk material enabling high deformability (up to 2000%) and good elastic recoverability (up to 80% at 50 °C above Tm,PCL). In the programmed thermoplastic actuators a high content of crystallizable PCL actuation domains ensures pronounced thermoreversible shape changes upon repetitive cooling and heating. The programmed actuator skeleton, composed of PCL crystals present at the upper actuation temperature Thigh and the remaining glassy PIBMD domains, enabled oriented crystallization upon cooling. The actuation performance of PIBMD-PCL could be tailored by balancing the interplay between actuation and skeleton, but also by varying the quantity of crystalline PIBMD hard domains via the copolymer composition, the applied programming strain, and the choice of Thigh. The actuator with 17 mol% PIBMD showed the highest reversible elongation of 11.4% when programmed to a strain of 900% at 50 °C. It is anticipated that the presented thermoplastic actuator materials can be applied as modern compression textiles. %0 conference poster %@ %A Mazurek-Budzynska, M.,Razzaq, M.,Noechel, U.,Behl, M.,Rokicki, G.,Lendlein, A. %D 2018 %J Advanced Functional Polymers for Medicine, AFPM 2018 %N %P %T Hydrolytic stability of aliphatic poly(carbonate-urea-urethane)s %U %X %0 journal article %@ 1616-5187 %A Peng, X.,Behl, M.,Zhang, P.,Mazurek-Budzyñska, M.,Feng, Y.,Lendlein, A. %D 2018 %J Macromolecular Bioscience %N 12 %P 1800257 %R doi:10.1002/mabi.201800257 %T Synthesis of Well-Defined Dihydroxy Telechelics by (Co)polymerization of Morpholine-2,5-Diones Catalyzed by Sn(IV) Alkoxide %U https://doi.org/10.1002/mabi.201800257 12 %X Well-defined dihydroxy telechelic oligodepsipeptides (oDPs), which have a high application potential as building blocks for scaffold materials for tissue engineering applications or particulate carrier systems for drug delivery applications are synthesized by ring-opening polymerization (ROP) of morpholine-2,5-diones (MDs) catalyzed by 1,1,6,6-tetra-n-butyl-1,6-distanna-2,5,7,10-tetraoxacyclodecane (Sn(IV) alkoxide). In contrast to ROP catalyzed by Sn(Oct)2, the usage of Sn(IV) alkoxide leads to oDPs, with less side products and well-defined end groups, which is crucial for potential pharmaceutical applications. A slightly faster reaction of the ROP catalyzed by Sn(IV) alkoxide compared to the ROP initiated by Sn(Oct)2/EG is found. Copolymerization of different MDs resulted in amorphous copolymers with T gs between 44 and 54 °C depending on the molar comonomer ratios in the range from 25% to 75%. Based on the well-defined telechelic character of the Sn(IV) alkoxide synthesized oDPs as determined by matrix-assisted laser desorption/ionization time of flight measurements, they resemble interesting building blocks for subsequent postfunctionalization or multifunctional materials based on multiblock copolymer systems whereas the amorphous oDP-based copolymers are interesting building blocks for matrices of drug delivery systems. %0 book part %@ %A Lendlein, A.,Razzaq, M.Y.,Wischke, C.,Kratz, K.,Heuchel, M.,Zotzmann, J.,Hiebl, B.,Neffe, A.T.,Behl, M. %D 2017 %J Comprehensive Biomaterials II - Reference Module in Materials Science and Materials Engineering, Metallic, Ceramic, and Polymeric Biomaterials %N %P 620-647 %R doi:10.1016/B978-0-12-803581-8.10213-9 %T Shape-Memory Polymers %U https://doi.org/10.1016/B978-0-12-803581-8.10213-9 %X This is an update of A. Lendlein, C. Wischke, K. Kratz, M. Heuchel, J. Zotzmann, B. Hiebl, A.T. Neffe and M. Behl, 1.126 – Shape-Memory Polymers. In Comprehensive Biomaterials, edited by Paul Ducheyne, Elsevier, Oxford, 2011, pp. 479–496.,Medical devices such as implants, surgical instruments, extracorporal devices, and wound covers, as well as controlled drug delivery systems (CDDS) require a specific combination of material properties and functions including, for example, mechanical stability, biocompatibility, and biofunctionality. Polymeric biomaterials are of high relevance for such applications, as properties and functions can be tuned in a wide range by only small defined variations of their chemical or morphological structure. The rapid progress in surgical techniques, especially in minimally invasive surgery, requires smart materials, which are capable of an active on-demand movement and which do not need to be removed in a second surgery. These challenges can be addressed by shape-memory polymers (SMPs) described in this chapter. SMPs are of high technological significance for biomedical applications as they enable on-demand predefined changes in the shape of a device upon exposure to a suitable stimulus such as heat or alternating magnetic field (AMF). Multifunctional materials are obtained when the shape-memory effect is combined with an additional function such as hydrolytic degradability, biofunctionality, and controlled drug release. Selected biomaterials with shape-memory capability are presented, including data on their biocompatibility. The potential of SMPs as a platform technology for biomedical applications is sketched by an overview on SMP-based medical devices being developed and the potential use of SMPs as matrix for CDDS. %0 journal article %@ 0001-4842 %A Löwenberg, C.,Balk, M.,Wischke, C.,Behl, M.,Lendlein, A. %D 2017 %J Accounts of Chemical Research %N 4 %P 723-732 %R doi:10.1021/acs.accounts.6b00584 %T Shape-Memory Hydrogels: Evolution of Structural Principles To Enable Shape Switching of Hydrophilic Polymer Networks %U https://doi.org/10.1021/acs.accounts.6b00584 4 %X The ability of hydrophilic chain segments in polymer networks to strongly interact with water allows the volumetric expansion of the material and formation of a hydrogel. When polymer chain segments undergo reversible hydration depending on environmental conditions, smart hydrogels can be realized, which are able to shrink/swell and thus alter their volume on demand. In contrast, implementing the capacity of hydrogels to switch their shape rather than volume demands more sophisticated chemical approaches and structural concepts.,In this Account, the principles of hydrogel network design, incorporation of molecular switches, and hydrogel microstructures are summarized that enable a spatially directed actuation of hydrogels by a shape-memory effect (SME) without major volume alteration. The SME involves an elastic deformation (programming) of samples, which are temporarily fixed by reversible covalent or physical cross-links resulting in a temporary shape. The material can reverse to the original shape when these molecular switches are affected by application of a suitable stimulus. Hydrophobic shape-memory polymers (SMPs), which are established with complex functions including multiple or reversible shape-switching, may provide inspiration for the molecular architecture of shape-memory hydrogels (SMHs), but cannot be identically copied in the world of hydrophilic soft materials. For instance, fixation of the temporary shape requires cross-links to be formed also in an aqueous environment, which may not be realized, for example, by crystalline domains from the hydrophilic main chains as these may dissolve in presence of water. Accordingly, dual-shape hydrogels have evolved, where, for example, hydrophobic crystallizable side chains have been linked into hydrophilic polymer networks to act as temperature-sensitive temporary cross-links. By incorporating a second type of such side chains, triple-shape hydrogels can be realized. Considering the typically given light permeability of hydrogels and the fully hydrated state with easy permeation by small molecules, other types of stimuli like light, pH, or ions can be employed that may not be easily used in hydrophobic SMPs. In some cases, those molecular switches can respond to more than one stimulus, thus increasing the number of opportunities to induce actuation of these synthetic hydrogels. Beyond this, biopolymer-based hydrogels can be equipped with a shape switching function when facilitating, for example, triple helix formation in proteins or ionic interactions in polysaccharides. Eventually, microstructured SMHs such as hybrid or porous structures can combine the shape-switching function with an improved performance by helping to overcome frequent shortcomings of hydrogels such as low mechanical strength or volume change upon temporary cross-link cleavage. Specifically, shape switching without major volume alteration is possible in porous SMHs by decoupling small volume changes of pore walls on the microscale and the macroscopic sample size. Furthermore, oligomeric rather than short aliphatic side chains as molecular switches allow stabilization of the sample volumes. Based on those structural principles and switching functionalities, SMHs have already entered into applications as soft actuators and are considered, for example, for cell manipulation in biomedicine. In the context of those applications, switching kinetics, switching forces, and reversibility of switching are aspects to be further explored. %0 conference poster %@ %A Assuncao, M.,Walter, M.,Bäckemo Johansson, J.,Topczewska, P.,Krüger-Genge, A.,Braune, S.,Roch, T.,Blocki, A.,Behl, M.,Jannasch, A.,Matschke, K.,Klopfleisch, R.,Jung, F.,Lendlein, A. %D 2017 %J 36. Jahrestagung der Deutschen Gesellschaft für Klinische Mikrozirkulation und Hämorheologie (DGKMH) %N %P %T Characterization of PCL-BA copolymer networks for application as vascular patch %U %X %0 journal article %@ 1022-1336 %A Chen, D.,Xia, X.,Wong, T.W.,Bai, H.,Behl, M.,Zhao, Q.,Lendlein, A.,Xie, T. %D 2017 %J Macromolecular Rapid Communications %N 7 %P 1600746 %R doi:10.1002/marc.201600746 %T Omnidirectional Shape Memory Effect via Lyophilization of PEG Hydrogels %U https://doi.org/10.1002/marc.201600746 7 %X Device applications of shape memory polymers demand diverse shape changing geometries, which are currently limited to non-omnidirectional movement. This restriction originates from traditional thermomechanical programming methods such as uniaxial, biaxial stretching, bending, or compression. A solvent-modulated programming method is reported to achieve an omnidirectional shape memory behavior. The method utilizes freeze drying of hydrogels of polyethylene glycol networks with a melting transition temperature around 50 °C in their dry state. Such a process creates temporarily fixed macroporosity, which collapses upon heating, leading to significant omnidirectional shrinkage. These shrunken materials can swell in water to form hydrogels again and the omnidirectional programming and recovery can be repeated. The fixity ratio (R f) and recovery ratio (R r) can be maintained at 90% and 98% respectively upon shape memory multicycling. The maximum linear recoverable strain, as limited by the maximum swelling, is ≈90%. Amongst various application potentials, one can envision the fabrication of multiphase composites by taking advantages of the omnidirectional shrinkage from a porous polymer to a denser structure. %0 conference lecture %@ %A Razzaq, M.,Behl, M.,Lendlein, A. %D 2017 %J MRS Spring Meeting 2017 %N %P %T Thermally-induced reversible bidirectional shape-memory effect of hybrid nanocomposites %U %X %0 book part %@ %A Heek, T.,Behl, M.,Lendlein, A. %D 2017 %J Handbook of Telechelic Polyesters, Polycarbonates, and Polyethers %N %P 115-183 %R doi:10.1201/9781315364469-5 %T Telechelic Poly(Epsilon-Caprolactone)s: Synthesis and Applications %U https://doi.org/10.1201/9781315364469-5 %X A key challenge of polymer chemistry is the synthesis and development of polymeric materials whose chemical and physical characteristics fit their intended field of application. In general, three distinct features of a polymer determine these properties: the chemical composition (i.e., the used (co‑)monomers)), the topology (e.g., linear, branched, network), and the nature and distribution of chemical functional groups, as these determine potential chemical reactivity or physical interactions with the environment. The combination of these design motifs is referred to as the polymer architecture [1]. A modification in one of these parameters can cause significant changes in the resulting properties of a certain polymer. %0 journal article %@ 2059-8521 %A Peng, X.,Behl, M.,Zhang, P.,Mazurek-Budzynska, M.,Feng, Y.,Lendlein, A. %D 2017 %J MRS Advances %N 47 %P 2551-2559 %R doi:10.1557/adv.2017.486 %T Synthesis and Characterization of Multiblock Poly(Ester-Amide-Urethane)s %U https://doi.org/10.1557/adv.2017.486 47 %X In this study, a multiblock copolymer containing oligo(3-methyl-morpholine-2,5-dione) (oMMD) and oligo(3-sec-butyl-morpholine-2,5-dione) (oBMD) building blocks obtained by ring-opening polymerization (ROP) of the corresponding monomers, was synthesized in a polyaddition reaction using an aliphatic diisocyanate. The multiblock copolymer (pBMD-MMD) provided a molecular weight of 40,000 g·mol−1, determined by gel permeation chromatography (GPC). Incorporation of both oligodepsipeptide segments in multiblock copolymers was confirmed by 1H NMR and Matrix Assisted Laser Desorption/Ionization Time Of Flight Mass Spectroscopy (MALDI-TOF MS) analysis. pBMD-MMD showed two separated glass transition temperatures (61 °C and 74 °C) indicating a microphase separation. Furthermore, a broad glass transition was observed by DMTA, which can be attributed to strong physical interaction i.e. by H-bonds formed between amide, ester, and urethane groups of the investigated copolymers. The obtained multiblock copolymer is supposed to own the capability to exhibit strong physical interactions. %0 conference lecture %@ %A Balk, M.,Behl, M.,Nöchel, U.,Lendlein, A. %D 2017 %J Polymers for Advanced Technologies Conference 2017 %N %P %T Complex movements enabled by triple-shape hydrogels %U %X Stimuli-sensitive hydrogels provide the ability to store large amounts of water, exhibit soft tissuelike,mechanical properties, and are capable to respond to a stimulus like temperature, changes in,pH, or a variation of the concentration of ions.[1] The strategy to incorporate crystallizable,switching segments as side chains in a hydrophilic polymer network resulted in hydrogels with on,demand directed movements when heat was applied, whereby constant degrees of swelling during,shape switches were obtained.[2],Here we report about hydrogels providing complex movements of soft materials with two almost,independent shape changes, which were triggered by a thermally-induced triple-shape effect.[3],Triple-shape hydrogels (TSHGs) with two different semi-crystalline switching segments integrated,as side chains were designed, whereby interferences of volume changes could be avoided as the,degrees of swelling were almost independent of different shapes and temperatures. Two distinct,shapes were implemented by a two-step programming procedure resulting in shape fixity ratios of,generally > 50%. While shorter side chains orient perpendicular to the hydrophilic main chain, side,chains with a higher molecular weight gain lower orientation after deformation as detected by,means of X-ray scattering. Furthermore, it was observed that the orientation of the switching,domains is not a key requirement for adequate shape fixity and recovery ratios of TSHGs.,Therefore, these soft materials, which provide complex directed movements, are potential material,candidates for two-step self-unfolding devices or soft temperature-sensitive actuators, e.g. smart,valves for flow rate control in an aqueous media. %0 journal article %@ 2059-8521 %A You, Z.,Behl, M.,Loewenberg, C.,Lendlein, A. %D 2017 %J MRS Advances %N 47 %P 2571-2579 %R doi:10.1557/adv.2017.491 %T pH-sensitivity and Conformation Change of the N-terminal Methacrylated Peptide VK20 %U https://doi.org/10.1557/adv.2017.491 47 %X N-terminal methacrylation of peptide MAX1, which is capable of conformational changes by variation of the pH, results in a peptide, named VK20. Increasing the reactivity of this terminal group enables further coupling reactions or chemical modifications of the peptide. However, this end group functionalization may influence the ability of conformational changes of VK20, as well as its properties. In this paper, the influence of pH on the transition between random coil and ß-sheet conformation of VK20, including the transition kinetics, were investigated. At pH values of 9 and higher, the kinetics of ß-sheet formation increased for VK20, compared to MAX1. The self-assembly into ß-sheets recognized by the formation of a physically crosslinked gel was furthermore indicated by a significant increase of G’. An increase in pH (from 9 to 9.5) led to a faster gelation of the peptide VK20. Simultaneously, G’ was increased from 460 ± 70 Pa (at pH 9) to 1520 ± 180 Pa (at pH 9.5). At the nanoscale, the gel showed a highly interconnected fibrillary network structure with uniform fibril widths of approximately 3.4 ± 0.5 nm (N=30). The recovery of the peptide conformation back to random coil resulted in the dissolution of the gel, whereby the kinetics of the recovery depended on the pH. Conclusively, the ability of MAX1 to undergo conformational changes was not affected by N-terminal methacrylation whereas the kinetics of pH-sensitive ß-sheet formations has been increased. %0 journal article %@ 2046-2069 %A Mazurek-Budzynska, M.,Razzaq, M.Y.,Rokicki, G.,Behl, M.,Lendlein, A. %D 2017 %J MRS Advances %N 47 %P 2529-2536 %R doi:10.1557/adv.2017.471 %T High-Strain Shape-Memory Properties of Poly(Carbonate-Urea-Urethane)s Based on Aliphatic Oligocarbonates and L-Lysine Diisocyanate %U https://doi.org/10.1557/adv.2017.471 47 %X The simultaneous capability of high-strain deformation and high shape recovery ratio constitutes a great challenge in design of the shape-memory polymers. Here we report on poly(carbonate-urea-urethane)s (PCUUs) synthesized by a precursor route, based on oligo(alkylene carbonate) diols, L-lysine diisocyanate (LDI), and water vapor. When programed with a strain of ε prog = 800%, the PCUU networks exhibited a one-way shape-memory effect (1W-SME) with excellent shape fixity (> 97%) and shape recovery (> 99%) ratios. The switching temperatures (T sw) varied between 50 and 56 °C and correlated to the melting transitions of the switching domains. The obtained PCUUs capable of high-strain are interesting candidate materials for degradable biomaterials as required in smart medical devices. %0 journal article %@ 1042-7147 %A Balk, M.,Behl, M.,Yang, J.,Li, Q.,Wischke, C.,Feng, Y.,Lendlein, A. %D 2017 %J Polymers for Advanced Technologies %N 10 %P 1278-1284 %R doi:10.1002/pat.3911 %T Design of polycationic micelles by self‐assembly of polyethyleneimine functionalized oligo[(ε‐caprolactone)‐co‐glycolide] ABA block copolymers %U https://doi.org/10.1002/pat.3911 10 %X Cationic polymeric micelles are of interest as delivery materials for nucleotides allowing condensation and transport of anionic macromolecules and enabling the reduction of cytotoxicity of polyethyleneimine, the current standard of vectors for non-viral nucleic acid delivery. In addition, micelles based on a degradable core would be capable to degrade hydrolytically and release their payload, which should preferably occur after uptake in early endosomes providing a pH of 5.5. We explored whether degradable and amphiphilic ABA block copolymers from hyperbranched polyethyleneimine A blocks and B blocks based on hydrophobic oligoesters (CG) can be created, which can degrade in a pH range relevant for the early endosomes. CG was synthesized by ring-opening polymerization of ε-caprolactone and diglycolide. Polycationic micelles with particle sizes between 19 ± 1 and 43 ± 2 nm were obtained by self-assembly of the ABA block copolymers with different chain lengths of B blocks and/or co-assembly with a diblock copolymer from poly(ethylene glycol) (PEG) functionalized CG oligoester in phosphate-buffered saline solution. Mixed micelles containing PEG-CG showed a decreased zeta potential, suggesting a shielding by dangling PEG chains at the micelle surfaces. Sizes of cationic micelles were stable at pH = 7.4 over the studied time period of 2 weeks at 37 °C. The hydrolytic degradation was controlled by the composition of the CG core and was accelerated when the pH was decreased to 5.5 as detected by increasing micelle sizes. In this way, the polycationic micelles may act as an on-demand delivery system of condensed macromolecules. %0 conference lecture %@ %A You, Z.,Behl, M.,Lendlein, A. %D 2017 %J MRS Spring Meeting 2017 %N %P %T Shape-memory cryogels based on conformational transition of peptides %U %X %0 journal article %@ 1042-7147 %A Mazurek-Budzynska, M.,Razzaq, M.Y.,Tomczyk, K.,Rokicki, G.,Behl, M.,Lendlein, A. %D 2017 %J Polymers for Advanced Technologies %N 10 %P 1285-1293 %R doi:10.1002/pat.3948 %T Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect %U https://doi.org/10.1002/pat.3948 10 %X A challenge in the design of shape-memory polymers (SMPs) is to achieve high deformability with a simultaneous high shape recovery ratio. Here we explored, whether SMPs featuring large deformation capability and high shape recovery ratios can be created as polymer networks providing two kinds of netpoints based on covalent bonds and physical interactions. As a model system, we selected poly(carbonate-urea-urethane)s (PCUUs) synthesized by a precursor route, based on oligo(alkylene carbonate) diols, isophorone diisocyanate (IPDI), and water vapor. The PCUU networks exhibited a one-way shape-memory effect (1W-SME) with programmed strains up to εprog = 1000% whereby they provided excellent shape fixity (92–97%) and shape recovery (≥99%) ratios. The switching temperatures (Tsw) varied between 36 and 65 °C and increased with the increasing molecular weight of the oligo(alkylene carbonate) diol and length of the hydrocarbon chain between the carbonate linkages. Tsw was also influenced by the strain applied during programming (εprog). Poly(carbonate-urethane)s have been reported to have good biocompatibility and biostability, which in the combination of high-strain capacity and high Young's modulus makes the obtained PCUUs interesting candidate materials suitable for medical devices such as medical sutures or vascular stents. %0 conference lecture %@ %A Behl, M. %D 2017 %J BIFTM PhD Symposium - BioInterfaces in Technology and Medicine %N %P %T Ring-opening polymerisation of biomaterials %U %X %0 conference lecture %@ %A Behl, M.,Balk, M.,Zhang, P.,Nöchel, U.,Lendlein, A. %D 2017 %J XXVI International Materials Research Congress 2017 %N %P %T Shape-memory hydrogels as a technology platform for soft actuators %U %X %0 journal article %@ 1042-7147 %A Yan, W.,Fang, L.,Weigel, T.,Behl, M.,Kratz, K.,Lendlein, A. %D 2017 %J Polymers for Advanced Technologies %N 10 %P 1339-1345 %R doi:10.1002/pat.3953 %T The influence of thermal treatment on the morphology in differently prepared films of a oligodepsipeptide based multiblock copolymer %U https://doi.org/10.1002/pat.3953 10 %X Degradable multiblock copolymers prepared from equal weight amounts of poly(ε-caprolactone)-diol (PCL-diol) and poly[oligo(3S-iso-butylmorpholine-2,5-dione)]-diol (PIBMD-diol), named PCL-PIBMD, provide a phase-segregated morphology. It exhibits a low melting temperature from PCL domains (Tm,PCL) of 38 ± 2 °C and a high Tm,PIBMD of 170 ± 2 °C with a glass transition temperature (Tg,PIBMD) at 42 ± 2 °C from PIBMD domains.,In this study, we explored the influence of applying different thermal treatments on the resulting morphologies of solution-cast and spin-coated PCL-PIBMD thin films, which showed different initial surface morphologies. Differential scanning calorimetry results and atomic force microscopy images after different thermal treatments indicated that PCL and PIBMD domains showed similar crystallization behaviors in 270 ± 30 µm thick solution-cast films as well as in 30 ± 2 and 8 ± 1 nm thick spin-coated PCL-PIBMD films. Existing PIBMD crystalline domains highly restricted the generation of PCL crystalline domains during cooling when the sample was annealed at 180 °C. By annealing the sample above 120 °C, the PIBMD domains crystallized sufficiently and covered the free surface, which restricted the crystallization of PCL domains during cooling. The PCL domains can crystallize by hindering the crystallization of PIBMD domains via the fast vitrification of PIBMD domains when the sample was cooled/quenched in liquid nitrogen after annealing at 180 °C. These findings contribute to a better fundamental understanding of the crystallization mechanism of multi-block copolymers containing two crystallizable domains whereby the Tg of the higher melting domain type is in the same temperature range as the Tm of the lower melting domain type. %0 conference poster %@ %A Zhang, P.,Behl, M.,Peng, X.,Razzaq, M.,Lendlein, A. %D 2017 %J MRS Spring Meeting 2017 %N %P %T Ultrasonic Cavitation Induced Shape-Memory Effect in Porous Polymer Networks %U %X %0 conference lecture %@ %A Behl, M.,Balk, M.,Lendlein, A. %D 2017 %J Polymers for Advanced Technologies Conference 2017 %N %P %T Robot Assisted Synthesis of Alternating Multiblock Copolymers Based on Oligo(ε-caprolactone)/Oligotetrahydrofuran %U %X %0 conference lecture %@ %A You, Z.,Behl, M.,Lendlein, A. %D 2017 %J BIFTM PhD Symposium - BioInterfaces in Technology and Medicine %N %P %T Conformational transition of peptide functionalized cryogels enabling shape-memory capability %U %X %0 conference poster %@ %A Peng, X.,Behl, M.,Zhang, P.,Lendlein, A. %D 2017 %J MRS Spring Meeting 2017 %N %P %T Decrease of Tg of polymers from morpholinediones by modification with hexyl groups %U %X %0 conference poster %@ %A Mazurek-Budzynska, M.,Razzaq, M.Y.,Tomczyk, K.,Rokicki, G.,Behl, M.,Lendlein, A. %D 2016 %J Integrating function into polymers, Polydays 2016 %N %P %T High-strain shape-memory effect of poly(carbonate-urea-urethane) networks %U %X %0 conference poster %@ %A Balk, M.,Behl, M.,Yang, J.,Li, Q.,Wischke, C.,Feng, Y.,Lendlein, A. %D 2016 %J Integrating function into polymers, Polydays 2016 %N %P %T Design of Polycationic Micelles by Self-Assembly of Polyethyleneimine Functionalized Oligo[(ε-aprolactone)-co-glycolide] ABA Block Copolymers %U %X %0 conference poster %@ %A Yan, W.,Behl, M.,Kratz, K.,Lendlein, A. %D 2016 %J Integrating function into polymers, Polydays 2016 %N %P %T Insights in the shape-memory mechanism of multiblock copolymers having crystallizable as well as glassy switching segments %U %X %0 conference lecture %@ %A Balk, M.,Behl, M.,Noechel, U.,Lendlein, A. %D 2016 %J Shape Memory Applications, Research and Technology Symposium, SMART 2016 %N %P %T 3D Structured Hydrogels with Enzymatically-Induced Shape Shifting %U %X %0 journal article %@ 2073-4360 %A Feng, Y.,Liu, W.,Ren, X.,Lu, W.,Guo, M.,Behl, M.,Lendlein, A.,Zhang, W. %D 2016 %J Polymers %N 3 %P 58 %R doi:10.3390/polym8030058 %T Evaluation of Electrospun PCL-PIBMD Meshes Modified with Plasmid Complexes in Vitro and in Vivo %U https://doi.org/10.3390/polym8030058 3 %X Functional artificial vascular meshes from biodegradable polymers have been widely explored for certain tissue engineered meshes. Still, the foreign body reaction and limitation in endothelialization are challenges for such devices. Here, degradable meshes from phase-segregated multiblock copolymers consisting of poly(ε-caprolactone) (PCL) and polydepsipeptide segments are successfully prepared by electrospinning and electrospraying techniques. The pEGFP-ZNF580 plasmid microparticles (MPs-pZNF580) were loaded into the electrospun meshes to enhance endothelialization. These functional meshes were evaluated in vitro and in vivo. The adhesion and proliferation of endothelial cells on the meshes were enhanced in loaded mesh groups. Moreover, the hemocompatibility and the tissue response of the meshes were further tested. The complete tests showed that the vascular meshes modified with MPs-pZNF580 possessed satisfactory performance with an average fiber diameter of 550 ± 160 nm, tensile strength of 27 ± 3 MPa, Young’s modulus of 1. 9 ± 0.2 MPa, water contact angle of 95° ± 2°, relative cell number of 122% ± 1% after 7 days of culture, and low blood platelet adhesion as well as weak inflammatory reactions compared to control groups. %0 journal article %@ 2059-8521 %A Baudis, S.,Balk, M.,Lendlein, A.,Behl, M. %D 2016 %J MRS Advances %N 27 %P 2003-2009 %R doi:10.1557/adv.2016.411 %T Robot Assisted Polyurethane Chain Extension of Dihydroxy Telechelic Depsipeptides %U https://doi.org/10.1557/adv.2016.411 27 %X Depsipeptide-based multiblock copolymers synthesized from dihydroxy telechelic oligodepsipeptide precursors are promising candidate materials for biomedical and pharmaceutical applications. High molecular weight polymers in polyaddition reactions e.g. of diols with diisocyanates can only be reached when reactive groups are equivalent and a high conversion for this step growth polymerization is obtained. However, in depsipeptide-based multiblock urethanes reported so far, the stoichiometric ratio of the diisocyanate compound exceeded the theoretical value of 100% by far. In order to investigate the influence of the dosing system in this unusual behavior of the stoichiometric reaction two dosing devices, a solid dosing unit (SDU) and a gravimetric dosing unit (GDU) were used for a gravimetric transfer of an oligo(3-sec-butylmorpholine-2.5-dione) (OBMD) as model oligodepsipeptide. The OBMD precursor, which was transferred as a solid or as a highly viscous solution, was reacted with an isomeric mixture of 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanate (TMDI) as chain extender. Two series of 49 reactions were performed and the chain extension efficacy of the building block was compared between the SDU and GDU as well as with respect to the Carothers equation. When the GDU was used the chain extension yielded higher molecular weights, proving the high accuracy of the dosing device, and the molar ratio of TMDI required for the high-throughput synthesis of the depsipeptide-based multiblock copolymers was similar to depsipeptide-based multiblock copolymers created in a classical synthesis approach. %0 journal article %@ 1944-8244 %A Nöchel, U.,Behl, M.,Balk, M.,Lendlein, A. %D 2016 %J ACS Applied Materials and Interfaces %N 41 %P 28068-28076 %R doi:10.1021/acsami.6b09581 %T Thermally-Induced Triple-Shape Hydrogels: Soft Materials Enabling Complex Movements %U https://doi.org/10.1021/acsami.6b09581 41 %X Shape-memory hydrogels enable directed movements of a specimen in response to temperature, whereby crystallizable switching segments incorporated as side chains resulted in constant degrees of swelling during the shape-memory cycle. Here we report about hydrogels exhibiting a thermally induced triple-shape effect that allows complex movements of soft materials with two almost independent shape changes. Potential applications for those soft triple-shape materials are two-step self-unfolding devices or temperature-sensitive hydrogel actuators, for example, smart valves for flow rate control in aqueous media. Series of hydrogels with two different hydrophobic crystallizable switching segments were prepared. The degrees of swelling of the triple-shape hydrogels were not affected for different shapes or temperatures, which avoided in this way interferences on the shape shifts. During the two-step programming procedure, two distinct shapes can be implemented as reflected by shape fixity ratios of generally >50%. Structural analysis of the switching domains during the triple-shape cycle by means of X-ray scattering indicates that longer side chains gain lower orientation after deformation and that shorter side chains orient perpendicular to the hydrophilic main chain. Furthermore, it is observed that increased orientation of the switching domains is not a key requirement for adequate shape fixity and recovery ratios of the triple-shape effect in hydrogels, thus longer side chains can be utilized as switching segments in other shape-memory hydrogels. %0 journal article %@ 2041-1723 %A Fuhrmann, A.,Goestl, R.,Wendt, R.,Koetteritzsch, J.,Hager, M.D.,Schubert, U.S.,Brademann-Jock, K.,Thuenemann, A.F.,Noechel, U.,Behl, M.,Hecht, S. %D 2016 %J Nature Communications %N %P 13623 %R doi:10.1038/ncomms13623 %T Conditional repair by locally switching the thermal healing capability of dynamic covalent polymers with light %U https://doi.org/10.1038/ncomms13623 %X Healable materials could play an important role in reducing the environmental footprint of our modern technological society through extending the life cycles of consumer products and constructions. However, as most healing processes are carried out by heat alone, the ability to heal damage generally kills the parent material’s thermal and mechanical properties. Here we present a dynamic covalent polymer network whose thermal healing ability can be switched ‘on’ and ‘off’ on demand by light, thereby providing local control over repair while retaining the advantageous macroscopic properties of static polymer networks. We employ a photoswitchable furan-based crosslinker, which reacts with short and mobile maleimide-substituted poly(lauryl methacrylate) chains forming strong covalent bonds while simultaneously allowing the reversible, spatiotemporally resolved control over thermally induced de- and re-crosslinking. We reason that our system can be adapted to more complex materials and has the potential to impact applications in responsive coatings, photolithography and microfabrication. %0 journal article %@ 0024-9297 %A Bilici, C.,Can, V.,Noechel, U.,Behl, M.,Lendlein, A.,Okay, O. %D 2016 %J Macromolecules %N 19 %P 7442-7449 %R doi:10.1021/acs.macromol.6b01539 %T Melt-Processable Shape-Memory Hydrogels with Self-Healing Ability of High Mechanical Strength %U https://doi.org/10.1021/acs.macromol.6b01539 19 %X We present here a synthetic strategy for the preparation of melt-processable shape-memory hydrogels with self-healing ability. The supramolecular hydrogel with a water content of 60–80 wt % consists of poly(acrylic acid) chains containing 20–50 mol % crystallizable n-octadecyl acrylate (C18A) segments together with surfactant micelles. The key of our approach to render the hydrogel melt-processable is the absence of chemical cross-links and the presence of surfactant micelles. At temperatures above the melting temperature Tm of the crystalline domains of alkyl side chains, the hydrogel liquefies due to the presence of surfactant micelles effective for solubilizing the hydrophobic C18A segments. At this stage, it can easily be shaped into any desired form by pouring into molds. Cooling below Tm and removing the surfactant from the gel network results in a hydrogel of any permanent shape with a particularly high compressive strength of 90 MPa and a Young’s modulus of 26 MPa. If the hydrogel was damaged on purpose e.g. by cutting into two pieces, the extraordinary mechanical properties can completely be recovered via temperature-induced healing process. The hydrogel also exhibits a complete shape fixity ratio and a shape recovery ratio of 97 ± 2%. %0 journal article %@ 0169-409X %A Balk, M.,Behl, M.,Wischke, C.,Zotzmann, J.,Lendlein, A. %D 2016 %J Advanced Drug Delivery Reviews %N %P 136-152 %R doi:10.1016/j.addr.2016.05.012 %T Recent advances in degradable lactide-based shape-memory polymers %U https://doi.org/10.1016/j.addr.2016.05.012 %X Biodegradable polymers are versatile polymeric materials that have a high potential in biomedical applications avoiding subsequent surgeries to remove, for example, an implanted device. In the past decade, significant advances have been achieved with poly(lactide acid) (PLA)-based materials, as they can be equipped with an additional functionality, that is, a shape-memory effect (SME). Shape-memory polymers (SMPs) can switch their shape in a predefined manner upon application of a specific external stimulus. Accordingly, SMPs have a high potential for applications ranging from electronic engineering, textiles, aerospace, and energy to biomedical and drug delivery fields based on the perspectives of new capabilities arising with such materials in biomedicine. This study summarizes the progress in SMPs with a particular focus on PLA, illustrates the design of suitable homo- and copolymer structures as well as the link between the (co)polymer structure and switching functionality, and describes recent advantages in the implementation of novel switching phenomena into SMP technology. %0 journal article %@ 0168-3659 %A Wang, W.,Balk, M.,Deng, Z.,Wischke, C.,Gossen, M.,Behl, M.,Ma, N.,Lendlein, A. %D 2016 %J Journal of Controlled Release %N %P 71-79 %R doi:10.1016/j.jconrel.2016.08.004 %T Engineering biodegradable micelles of polyethylenimine-based amphiphilic block copolymers for efficient DNA and siRNA delivery %U https://doi.org/10.1016/j.jconrel.2016.08.004 %X Polycationic micelles have shown advantageous properties as nucleic acid delivery vectors both in vitro and in vivo. In contrast to polycationic micelles reported so far, we designed particles integrating a sufficient nucleic acid condensation capability by polycationic polyethylenimine (PEI) segments as well as only a mild cytotoxic behavior. The micelles composed of a hydrophobic oligoester core with glycolide units resulting in fast degradation after cellular internalization in combination with PEG moieties acting as shielding agents. By grafting branched 25 kDa polyethylenimine (PEI25) and poly(ethylene glycol) (PEG) on poly[(ε-caprolactone)-co-glycolide] (CG), amphiphilic PEI-CG-PEI and PEG-CG block copolymers were used to form a series of micelles via self-assembly of PEI-CG-PEI or co-assembly of both copolymers for DNA and siRNA delivery. This modular system enabled a systematic investigation of different parameters and their synergetic effects as different functions were introduced. The polyplex formation and serum stability, cytotoxicity, and transfection activity could be tailored by changing the CG chain length in PEI-based copolymer, incorporating PEG-CG, and varying the N/P ratio. All micelle-based polyplex compositions showed high DNA transfection activity according to reporter gene-expression and an exceptionally high knockdown in siRNA delivery experiments. Remarkably, the GFP expression of > 99% cells was successfully knocked down by micelle-mediated siRNA interference, resulting in a decrease of two orders of magnitude in fluorescence intensity. Incorporation of PEG-CG in the micelles reduced the PEI-related cytotoxicity, and markedly enhanced the serum stability of both DNA and siRNA polyplexes. Compared with homo-PEI25, these micelles showed several advantages including the lower toxicity, higher siRNA transfection efficiency and higher polyplex stability in the presence of serum. This study therefore provides an effective approach to tune the structure, property and function of polycationic micelles for efficient DNA and siRNA delivery, which could contribute to the design and development of novel non-viral transfection vectors with superb functionality. %0 conference lecture %@ %A Lendlein, A.,Neffe, A.T.,Ma, N.,Behl, M.,Wischke, C. %D 2016 %J Multifunctional Biomaterials for Medicine, HVI Symposium 2016 %N %P %T Functional Polymers and Carriers Systems %U %X %0 journal article %@ 2059-8521 %A Balk, M.,Behl, M.,Noechel, U.,Lendlein, A. %D 2016 %J MRS Advances %N 27 %P 2011-2017 %R doi:10.1557/adv.2016.414 %T Architectured Shape-Memory Hydrogels with Switching Segments Based on Oligo(Epsilon-caprolactone) %U https://doi.org/10.1557/adv.2016.414 27 %X Shape-memory hydrogels (SMHs) are potential candidate materials for biomedical applications as they can mimic the elastic properties of soft tissue and exhibit shape transformations at body temperature. Here we explored, whether architectured SMHs can be designed by incorporating oligo(ε-caprolactone) (OCL, = 4500 g·mol-1, T m = 54 °C) side chains as switching segment into hydrophilic polymer networks based on N-vinylpyrrolidone as backbone forming component and oligo(ethylene glycol)divinylether (OEGDVE, = 250 g·mol-1) as crosslinker. By utilizing NaCl and NaHCO3 as porogene during thermal crosslinking architectured hydrogels having pore diameters between 30 and 500 µm and wall thicknesses ranging from 10 to 190 µm in the swollen state were synthesized. According to the porous microstructure, a macroscopic form stability was obtained when the polymer networks were swollen until equilibrium in water. Material properties were investigated as function of the OCL content, which was varied between 20 and 40 wt%. In compression experiments the architectured hydrogels exhibited strain fixity and strain recovery ratios above 80%. These architectured SMHs might enable biomaterial applications as smart implants with the recovery of bulky structures from compact shapes. %0 conference poster %@ %A Peng, X.,Behl, M.,Zhang, P.,Lendlein, A. %D 2016 %J International Conference on Dermal Drug Delivers by Nanocarrierrs, SFB Konferenz %N %P %T Morpholine-2,5-diones with hexyl side chains as monomers for oligodepsipeptides with decreased glass transition temperature %U %X %0 journal article %@ 0032-3861 %A Peng, X.,Behl, M.,Zhang, P.,Mazurek-Budzynska, M.,Razzaq, M.Y.,Lendlein, A. %D 2016 %J Polymer %N %P 318-326 %R doi:10.1016/j.polymer.2016.10.033 %T Hexyl-modified morpholine-2,5-dione-based oligodepsipeptides with relatively low glass transition temperature %U https://doi.org/10.1016/j.polymer.2016.10.033 %X Oligodepsipeptides (oDPs), alternating copolymers of an α-amino acid and an α-hydroxy acid, are typically created by ring-opening polymerization (ROP) of morpholine-2,5-dione derivatives (MDs). In general, oDPs exhibit relatively high glass transition temperatures (Tgs) caused by the strong intermolecular H-bonding between amide and ester bonds. So far, it was not reported that variation at α-amino acid moieties in MDs monomers lead to lower Tg. Here we explored whether the thermal properties of the oDPs can be adjusted by introducing a hexyl side chain in the α-hydroxy acid part of the MDs. By synthesizing a MD with an atactic pendant hexyl group at position 3, the influence of a modification at position 6 compared to a modification at position 3 towards ROP was investigated. In both cases the atactic bulky side groups hindered the H-bonding between chain segments resulting in a significant reduction of the Tgs to a temperature around human body temperature (32 and 36 °C) in contrast to ROP of a MD providing a methyl group at position 3 and a Tg ≈ 65 °C. Such oDPs could be interesting candidate materials for biomedical applications such as degradable implants. %0 conference lecture %@ %A Lendlein, A.,Neffe, A.T.,Ma, N.,Behl, M.,Wischke, C. %D 2016 %J International Conference on Dermal Drug Delivers by Nanocarrierrs, SFB Konferenz %N %P %T Functional Polymers and Carriers Systems %U %X %0 conference poster %@ %A Balk, M.,Behl, M.,Yang, J.,Li, Q.,Wischke, C.,Feng, Y.,Lendlein, A. %D 2016 %J Advanced Functional Polymers for Medicine, AFPM 2016 %N %P %T Design of Polycationic Micelles by Self-Assembly of Polyethyleneimine Functionalized Oligo[(ε-caprolactone)-co-glycolide] ABA Block Copolymers %U %X %0 conference poster %@ %A Mazurek-Budzynska, M.,Tomczyk, K.,Rokicki, G.,Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2016 %J Advanced Functional Polymers for Medicine, AFPM 2016 %N %P %T Poly(carbonate-urea-urethane) networks exhibiting high-strain shape memory effect %U %X %0 conference lecture %@ %A Kratz, K.,Noechel, U.,Behl, M.,Lendlein, A. %D 2016 %J Shape Memory Applications, Research and Technology Symposium, SMART 2016 %N %P %T Decoding Temperature - Memory Effects in Copolymer Networks Having Crystallizable Controlling Units %U %X %0 conference lecture %@ %A Behl, M.,Noechel, U.,Balk, M.,Lendlein, A. %D 2016 %J Shape Memory Applications, Research and Technology Symposium, SMART 2016 %N %P %T Thermally- induced Triple-shape Hydrogels %U %X %0 conference lecture (invited) %@ %A Behl, M.,Neffe, A.,Kratz, K.,Ma, N.,Lendlein, A. %D 2016 %J Medtec Europe %N %P %T Design Principles of Multifunctional Materials Interacting With Cells %U %X %0 journal article %@ 1022-1336 %A Zhang, P.,Behl, M.,Peng, X.,Razzaq, M.,Lendlein, A. %D 2016 %J Macromolecular Rapid Communications %N 23 %P 1897-1903 %R doi:10.1002/marc.201600439 %T Ultrasonic Cavitation Induced Shape-Memory Effect in Porous Polymer Networks %U https://doi.org/10.1002/marc.201600439 23 %X Inspired by the application of ultrasonic cavitation based mechanical force (CMF) to open small channels in natural soft materials (skin or tissue), it is explored whether an artificial polymer network can be created, in which shape-changes can be induced by CMF. This concept comprises an interconnected macroporous rhodium-phosphine (Rh-P) coordination polymer network, in which a CMF can reversibly dissociate the Rh-P microphases. In this way, the ligand exchange of Rh-P coordination bonds in the polymer network is accelerated, resulting in a topological rearrangement of molecular switches. This rearrangement of molecular switches enables the polymer network to release internal tension under ultrasound exposure, resulting in a CMF-induced shape-memory capability. The interconnected macroporous structure with thin pore walls is essential for allowing the CMF to effectively permeate throughout the polymer network. Potential applications of this CMF-induced shape-memory polymer can be mechanosensors or ultrasound controlled switches. %0 conference lecture (invited) %@ %A Behl, M.,Lendlein, A. %D 2016 %J Medizin Innovativ - MedTech Summit 2016 %N %P %T Bedeutung von Materialinnovationen für Gesundheit und Lebensqualität %U %X %0 journal article %@ 1946-4274 %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2015 %J MRS Online Proceedings Library %N %P 71-76 %R doi:10.1557/opl.2015.495 %T Thermally Controlled Shape-Memory Investigations of Nanocomposites Based on Oligo(ω-pentadecalactone) and Magnetic Nanoparticles Acting as Crosslinks %U https://doi.org/10.1557/opl.2015.495 %X Covalent integration of inorganic nanoparticles into polymer matrices leads to a homogenization of their distribution and enhances the structural properties. Here, we report on a thermally-controlled reversible shape-memory effect (R-SME) of magnetic nanocomposites under stress-controlled conditions. The magnetic nanocomposites consisted of an oligo(ω-pentadecalactone) (OPDL) matrix with covalently integrated or physically added magnetic nanoparticles (MNP). The R-SME of these materials was based on crystallization-induced elongation (CIE) and melting-induced contraction (MIC) under a constant stress in thermomechanical experiments. Furthermore, the adjustability of the recovery stress in magnetic nanocomposites as a function of MNP content was investigated. A slight increase in the recovery stress from 0.9 MPa for pure OPDL network to 1.2 MPa for H-NC containing 9 wt% of covalently integrated MNP was observed. %0 journal article %@ 1946-4274 %A Baudis, S.,Lendlein, A.,Behl, M. %D 2015 %J MRS Online Proceedings Library %N %P 109-115 %R doi:10.1557/opl.2015.493 %T Robot Assisted Synthesis and Characterization of Polyester-based Polyurethanes %U https://doi.org/10.1557/opl.2015.493 %X Dihydroxy telechelics are precursors for the synthesis of multiblock copolymers. In order to synthesize high molecular weight polymers with good elastic properties it is necessary to gain detailed knowledge of the reaction behavior of these precursors. Therefore it was explored whether the polyaddition reaction of polyester-diols can be established in a robotic synthesizer platform to facilitate the elucidation of reaction characteristics. A series of 16 reactions was performed using a telechelic polyester and trimethylhexamethylene diisocyanate. The chain extension behavior of the building block was compared with respect to the Carothers equation. It was found, that the chain extension behavior follows the expected trend. The molecular weight of the polymers increased when the optimal ratio of reactive groups was approached. %0 journal article %@ 2050-7488 %A Noechel, U.,Reddy, C.S.,Wang, K.,Cui, J.,Zizak, I.,Behl, M.,Kratz, K.,Lendlein, A. %D 2015 %J Journal of Materials Chemistry A %N 16 %P 8284-8293 %R doi:10.1039/C4TA06586G %T Nanostructural changes in crystallizable controlling units determine the temperature-memory of polymers %U https://doi.org/10.1039/C4TA06586G 16 %X Temperature-memory polymers remember the temperature, where they were deformed recently, enabled by broad thermal transitions. In this study, we explored a series of crosslinked poly[ethylene-co-(vinyl acetate)] networks (cPEVAs) comprising crystallizable polyethylene (PE) controlling units exhibiting a pronounced temperature-memory effect (TME) between 16 and 99 °C related to a broad melting transition ([similar]100 °C). The nanostructural changes in such cPEVAs during programming and activation of the TME were analyzed via in situ X-ray scattering and specific annealing experiments. Different contributions to the mechanism of memorizing high or low deformation temperatures (Tdeform) were observed in cPEVA, which can be associated to the average PE crystal sizes. At high deformation temperatures (>50 °C), newly formed PE crystals, which are established during cooling when fixing the temporary shape, dominated the TME mechanism. In contrast, at low Tdeform (<50 °C), corresponding to a cold drawing scenario, the deformation led preferably to a disruption of existing large crystals into smaller ones, which then fix the temporary shape upon cooling. The observed mechanism of memorizing a deformation temperature might enable the prediction of the TME behavior and the knowledge based design of other TMPs with crystallizable controlling units. %0 journal article %@ 1946-4274 %A Noechel, U.,Kratz, K.,Behl, M.,Lendlein, A. %D 2015 %J MRS Online Proceedings Library %N %P 41-48 %R doi:10.1557/opl.2015.427 %T Relation -between Nanostructural Changes and Macroscopic Effects during Reversible Temperature-Memory Effect under Stress-Free Conditions in Semicrystalline Polymer Networks %U https://doi.org/10.1557/opl.2015.427 %X Temperature-memory effects in polymers under stress-free conditions are typically limited to one way effects. Recently, crosslinked polymer networks comprising crystallizable domains, which were capable of a reversible temperature-memory effect (rTME) under stress-free conditions, were introduced. The utilization of crystallizable actuator domains (AD) and shape determining domains (SD) where related to two different temperature ranges of a single broad melting temperature transition in case of rTME. In this study we investigated the nanostructure of crosslinked poly[ethylene-co-(vinyl acetate)] cPEVA capable of rTME in situ during actuation cycles utilizing X-ray scattering techniques and related the changes on the nanoscale to effects on the macroscopic scale. It was observed that 23% of SD obtained at a separation temperature of 75 °C gave the highest reversible strain and when exceeding 80 °C only isotropic crystallization occurred and no rTME was observed. Furthermore, distances between oriented crystalline lamellae correlated to the macroscopic actuation during heating-cooling cycles, exhibiting long-periods from 14 to 17 nm as function of temperature. %0 journal article %@ 1022-1336 %A Saatchi, M.,Behl, M.,Noechel, U.,Lendlein, A. %D 2015 %J Macromolecular Rapid Communications %N 10 %P 880-884 %R doi:10.1002/marc.201400729 %T Copolymer Networks From Oligo(Epsilon-caprolactone) and n-Butyl Acrylate Enable a Reversible Bidirectional Shape-Memory Effect at Human Body Temperature %U https://doi.org/10.1002/marc.201400729 10 %X Exploiting the tremendous potential of the recently discovered reversible bidirectional shape-memory effect (rbSME) for biomedical applications requires switching temperatures in the physiological range. The recent strategy is based on the reduction of the melting temperature range (ΔT m) of the actuating oligo(ε-caprolactone) (OCL) domains in copolymer networks from OCL and n-butyl acrylate (BA), where the reversible effect can be adjusted to the human body temperature. In addition, it is investigated whether an rbSME in the temperature range close or even above Tm,offset (end of the melting transition) can be obtained. Two series of networks having mixtures of OCLs reveal broad ΔTms from 2 °C to 50 °C and from −10 °C to 37 °C, respectively. In cyclic, thermomechanical experiments the rbSME can be tailored to display pronounced actuation in a temperature interval between 20 °C and 37 °C. In this way, the application spectrum of the rbSME can be extended to biomedical applications. %0 journal article %@ 1751-6161 %A Guglielmi, P.O.,Herbert, E.G.,Tartivel, L.,Behl, M.,Lendlein, A.,Huber, N.,Lilleodden, E.T. %D 2015 %J Journal of the Mechanical Behavior of Biomedical Materials %N %P 1-10 %R doi:10.1016/j.jmbbm.2015.02.009 %T Mechanical characterization of oligo(ethylene glycol)-based hydrogels by dynamic nanoindentation experiments %U https://doi.org/10.1016/j.jmbbm.2015.02.009 %X Oligo(ethylene glycol)-based (OEG) hydrogel samples of varying cross-link densities and degrees of swelling were characterized through dynamic nanoindentation testing. Experiments were performed using a non-standard nanoindentation method, which was validated on a standard polystyrene sample. This method maximizes the capability of the instrument to measure the stiffness and damping of highly compliant, viscoelastic materials. Experiments were performed over the frequency range of 1 to 50 Hz, using a 1 mm diameter flat punch indenter. A hydration method was adopted to avoid sample dehydration during testing. Values of storage modulus (E′)(E′) ranged from 3.5 to 8.9 MPa for the different OEG-hydrogel samples investigated. Samples with higher OEG concentrations showed greater scatter in the modulus measurements and it is attributed to inhomogeneities in these materials. The (E′)(E′) values did not show a strong variation over frequency for any of the samples. Values of loss modulus (E″)(E″) were two orders of magnitude lower than the storage modulus, resulting in very low values of loss factor (E″/E′E″/E′<0.1). These are characteristics of strong gels, which present negligible viscous properties. %0 journal article %@ 0032-3861 %A Heuchel, M.,Razzaq, M.Y.,Kratz, K.,Behl, M.,Lendlein, A. %D 2015 %J Polymer %N %P 215-222 %R doi:10.1016/j.polymer.2015.03.063 %T Modeling the heat transfer in magneto-sensitive shape-memory polymer nanocomposites with dynamically changing surface area to volume ratios %U https://doi.org/10.1016/j.polymer.2015.03.063 %X Magneto-sensitive shape-memory polymer nanocomposites (SMPNCs) enable non-contact actuation of a shape-memory effect (SME) by inductive heating in an alternating magnetic field (AMF). Hereby, the achievable temperature (Tmax) at fixed magnetic field strength (H) and frequency is depending on the amount and type of incorporated magnetic fillers as well as on surface area to volume (S/V) ratio of the test specimen.,Here we present a heat transfer model for predicting Tmax of SMPNCs samples with different S/V ratios when exposed to an AMF. The obtained temperature difference between sample and surrounding in an AMF of constant magnetic field strength decreases at uni-axial deformation with the square root of the stretching ratio. The model was validated with magnetically heating experiments of two different SMPNC systems (comprising crystallizable or amorphous switching segments) containing the same magnetic nanoparticles, while H was varied from 7 to 27 kA m−1 at a fixed frequency of 258 kHz. The experimentally achieved temperatures at deformations up to 50% could be predicted with a divergence below 6%. Finally the model was applied in a principle design study of a device consisting of a rolled SMPNC stripe, which was stepwise opened by increasing H. The modeling approach might be helpful to predict the temperature profiles of SMPNCs which were heated by other mechanisms, e.g., radiofrequency or near IR. %0 journal article %@ 0939-6411 %A Mathew, S.,Baudis, S.,Neffe, A.T.,Behl, M.,Wischke, C.,Lendlein, A. %D 2015 %J European Journal of Pharmaceutics and Biopharmaceutics A %N %P 18-26 %R doi:10.1016/j.ejpb.2015.03.025 %T Effect of diisocyanate linkers on the degradation characteristics of copolyester urethanes as potential drug carrier matrices %U https://doi.org/10.1016/j.ejpb.2015.03.025 %X In this study, the effect of three aliphatic diisocyanate linkers, L-lysine diisocyanate ethyl ester (LDI), hexamethylene diisocyanate (HDI), and racemic 2,2,4-/2,4,4-trimethyl hexamethylene diisocyanate (TMDI), on the degradation of oligo[(rac-lactide)-co-glycolide] (64:36 mol%) based polyester urethanes (PEU) was examined. Samples were characterized for their molecular weight, mass loss, water uptake, sequence structure, and thermal and mechanical properties. Compared to non-segmented PLGA, the PEU showed higher water uptake and generally degraded faster. Interestingly, the rate of degradation was not directly correlating with the hydrophilicity of the diisocyanate moieties; instead, competing intra-/intermolecular hydrogen bonds in between urethane moieties appear to substantially decrease the rate of degradation for LDI-derived PEU. By comparing microparticles (μm) and films (mm) as matrices of different dimensions, it was shown that autocatalysis remains a contributor to degradation of the larger-sized PEU matrices as it is typical for non-segmented lactide/glycolide copolymers. The shown capacity of lactide/glycolide-based multiblock copolymers to degrade faster than PLGA and exhibit improved elastic properties could be of interest for medical implants and drug release systems. %0 journal article %@ 1946-4274 %A Heuchel, M.,Al-Qaisi, L.,Kratz, K.,Noechel, U.,Behl, M.,Lendlein, A. %D 2015 %J MRS Online Proceedings Library %N %P 127-134 %R doi:10.1557/opl.2015.527 %T Thermomechanical Characterization of a Series of Crosslinked Poly[ethylene-co-(vinyl acetate)] (PEVA) Copolymers %U https://doi.org/10.1557/opl.2015.527 %X Crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) has been recently introduced as a polymer material, which can be functionalized with various shape-memory effects by solely altering the thermomechanical treatment called programming.,In this study two series of cPEVAs with different vinyl acetate contents of 18 wt% (cPEVA18) and 28 wt% (cPEVA28) comprising different crosslink densities were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) in the temperature range of -130 °C to 120 °C. DMTA tests were performed in torsion mode, because such movements are highly relevant in the context of complex shape changes in shape-memory polymer based devices. Finally, the obtained DMTA results were compared with DMTA conducted in tension mode. Swelling experiments revealed a gel content in the range from 81% to 90% for cPEVA18 samples while for cPEVA28s a complete conversion was observed. The degree of swelling was found to decrease substantially with increasing crosslink density for both cPEVA series.,The influence of VA content and extent of crosslinking on the appearance of the respective melting (Tm) and glass transition (Tg) as well as the thermomechanical properties of cPEVA systems could be demonstrated by discussing both DSC and DMTA results. The temperature range of mechanical stability correlates with the VA content and is determined by decreasing Tm values. The cross links do barely alter the stiffness of a PEVA up to the Tm rang, but lead to constant mechanical rigidity in the rubbery range above Tm. %0 journal article %@ 1386-0291 %A Wang, W.,Kratz, K.,Behl, M.,Yan, W.,Liu, Y.,Xu, X.,Baudis, S.,Li, Z.,Kurtz, A.,Lendlein, A.,Ma, N. %D 2015 %J Clinical Hemorheology and Microcirculation %N 2 %P 301-321 %R doi:10.3233/CH-152001 %T The interaction of adipose-derived human mesenchymal stem cells and polyether ether ketone %U https://doi.org/10.3233/CH-152001 2 %X Polyether ether ketone (PEEK) as a high-performance, thermoplastic implant material entered the field of medical applications due to its structural function and commercial availability. In bone tissue engineering, the combination of mesenchymal stem cells (MSCs) with PEEK implants may accelerate the bone formation and promote the osseointegration between the implant and the adjacent bone tissue. In this concept the question how PEEK influences the behaviour and functions of MSCs is of great interest. Here the cellular response of human adipose-derived MSCs to PEEK was evaluated and compared to tissue culture plate (TCP) as the reference material. Viability and morphology of cells were not altered when cultured on the PEEK film. The cells on PEEK presented a high proliferation activity in spite of a relatively lower initial cell adhesion rate. There was no significant difference on cell apoptosis and senescence between the cells on PEEK and TCP. The inflammatory cytokines and VEGF secreted by the cells on these two surfaces were at similar levels. The cells on PEEK showed up-regulated BMP2 and down-regulated BMP4 and BMP6 gene expression, whereas no conspicuous differences were observed in the committed osteoblast markers (BGLAP, COL1A1 and Runx2). With osteoinduction the cells on PEEK and TCP exhibited a similar osteogenic differentiation potential. Our results demonstrate the biofunctionality of PEEK for human MSC cultivation and differentiation. Its clinical benefits in bone tissue engineering may be achieved by combining MSCs with PEEK implants. These data may also provide useful information for further modification of PEEK with chemical or physical methods to regulate the cellular processes of MSCs and to consequently improve the efficacy of MSC-PEEK based therapies. %0 journal article %@ 1042-7147 %A Goers, J.,Roch, T.,Tartivel, L.,Behl, M.,Ma, N.,Lendlein, A. %D 2015 %J Polymers for Advanced Technologies %N 12 %P 1378-1386 %R doi:10.1002/pat.3676 %T Immuno-compatibility of amphiphilic ABA triblock copolymer-based hydrogel films for biomedical applications %U https://doi.org/10.1002/pat.3676 12 %X The protein adsorption and immuno-compatibility of hydrogels largely influence the clinical outcome in biomedical application scenarios. In this study photo-crosslinked 2-isocyanate ethyl methacrylate–functionalized oligo(ethylene glycol)–oligo(propylene glycol)–oligo(ethylene glycol) (IEMA–OEG–OPG–OEG–IEMA)-based polymer hydrogel films were explored with respect to endotoxin contaminations, intrinsic immuno-modulatory features, and protein adsorption of human fibronectin as well as serum albumin. Therefore three different hydrogel films were prepared from aqueous solutions of dimethacrylated OEG–OPG–OEG triblock copolymers (Mn = 12,700 g mol−1, 70 mol% OEG content) with varying wt% of the macromonomer (10 to 30%) resulting in polymeric networks, which differ in their crosslinking density and accordingly their physical properties. It could be shown that all three hydrogel film compositions do not cause complement and immune cell activation. The films were protein repellent, but reversible protein diffusion in and out of the hydrogel network, depending on the mesh size of the network, could be observed. In conclusion, the hydrogels can be considered as immuno-compatible, which qualifies them for biomedical applications such as drug release systems. %0 journal article %@ 2192-2640 %A Li, Q.,Shi, C.,Zhang, W.,Behl, M.,Lendlein, A.,Feng, Y. %D 2015 %J Advanced Healthcare Materials %N 8 %P 1225-1235 %R doi:10.1002/adhm.201400817 %T Nanoparticles Complexed with Gene Vectors to Promote Proliferation of Human Vascular Endothelial Cells %U https://doi.org/10.1002/adhm.201400817 8 %X Amphiphilic block copolymers containing biodegradable hydrophobic segments of depsipeptide based copolymers have been synthesized and explored as gene carriers for enhancing proliferation of endothelial cells in vitro. These polymers form nanoparticles (NPs) with positive charges on their surface, which could condense recombinant plasmids of enhanced green fluorescent protein plasmid and ZNF580 gene (pEGFP-ZNF580) and protect them against DNase I. ZNF580 gene is efficiently transported into EA.hy926 cells to promote their proliferation, whereby the transfection efficiency of NPs/pEGFP-ZNF580 is approximately similar to that of Lipofectamine 2000. These results indicate that the NPs might have potential as a carrier for pEGFP-ZNF580, which could support endothelialization of cardiovascular implants. %0 conference lecture %@ %A Lv, J.,Hao, X.,Yang, J.,Feng, Y.,Behl, M.,Lendlein, A. %D 2015 %J 3rd Symposium on Innovative Polymers for Controlled Delivery, SIPCD 2014 %N %P %T PEI modified biodegradable complex micelles as gene transfer vector for proliferation of ECs %U %X %0 journal article %@ 0168-3659 %A Lv, J.,Hao, X.,Yang, J.,Feng, Y.,Behl, M.,Lendlein, A. %D 2015 %J Journal of Controlled Release %N %P e 60 %R doi:10.1016/j.jconrel.2015.05.099 %T PEI modified biodegradable complex micelles as gene transfer vector for proliferation of ECs %U https://doi.org/10.1016/j.jconrel.2015.05.099 %X No abstract %0 conference lecture %@ %A Wang, W.,Kratz, K.,Behl, M.,Yan, W.,Liu, Y.,Xu, X.,Baudis, S.,Li, Z.,Kurtz, A.,Lendlein, A.,Ma, N. %D 2015 %J 34th Conference of the German Society for Clinical Microcirculation and Hemorheology %N %P %T The interaction of adipose-derived human mesenchymal stem cells and polyether ether ketone %U %X %0 journal article %@ 0168-3659 %A Hao, X.,Lv, J.,Li, Q.,Fan, J.,Feng, Y.,Behl, M.,Lendlein, A. %D 2015 %J Journal of Controlled Release %N %P e 123 %R doi:10.1016/j.jconrel.2015.05.207 %T REDV-linked biodegradable polymeric micelles as the transfer vector of ZNF580 for the proliferation of endothelial cells %U https://doi.org/10.1016/j.jconrel.2015.05.207 %X No abstract %0 conference lecture %@ %A Wang, W.,Kratz, K.,Behl, M.,Xu, X.,Baudis, S.,Li, Z.,Kurtz, A.,Ma, N.,Lendlein, A. %D 2015 %J 34. Jahrestagung der Deutschen Gesellschaft für klinische Mikrozirkulation und Hämorheologie (DGKMH) %N %P %T The interaction of human adipose-derived mesenchymal stem cells and polyether ether ketone %U %X %0 conference lecture (invited) %@ %A Behl, M.,Saatchi, M.,Noechel, U.,Lendlein, A. %D 2015 %J 13th Int. Conference of Polymers for Advanced Technologies (PAT 2015) %N %P %T Reversible Bidirectional Shape-Memory Effect at Physiological Temperature from Oligo(epsilon-caprolactone) and n-Butyl Acrylate %U %X %0 conference lecture (invited) %@ %A Behl, M.,Saatchi, M.,Nöchel, U.,Lendlein, A. %D 2015 %J Lecture at the Tianjin University %N %P %T Bidirectional shape-memory effect at human body temperature %U %X %0 conference lecture %@ %A Behl, M.,Baudis, S.,Lendlein, A. %D 2015 %J MRS Fall Meeting 2015 %N %P %T Investigation of the Influence of Reaction Parameters on the Diameter of Copolymer Particles %U %X %0 conference lecture %@ %A Behl, M. %D 2015 %J Vortragstagung Polymerforschung in Berlin-Brandenburg %N %P %T Principles for the rationale design of biomaterials %U %X %0 conference poster %@ %A Görs, J.,Tartivel, L.,Roch, T.,Ma, N.,Behl, M.,Lendlein, A. %D 2015 %J Advanced Functional Polymers for Medicine (AFPM) %N %P %T Immuno-compatibility of Amphiphilic ABA Triblock Copolymer Based Hydrogel Films for Biomedical Application %U %X %0 conference lecture %@ %A Balk, M.,Behl, M.,Nöchel, U.,Lendlein, A. %D 2015 %J MRS Fall Meeting 2015 - Multifunctionality in Polymer-Based Materials; Gels and Interfaces %N %P %T 3D Structured Shape-Memory Hydrogels with Switching Segments Based on Oligo (ε-caprolactone) %U %X %0 conference poster %@ %A Rottke, F.,Schulz, B.,Richau, K.,Kratz, K.,Behl, M.,Lendlein, A. %D 2015 %J 9th Workshop on Ellipsometry (WSE 2015) %N %P %T Visualization of inhomogeneous; biodegradable polymeric Langmuir AClayers by imaging ellipsometry and mapping technique %U %X %0 conference lecture %@ %A Feng, Y.,Wang, H.,Lv, J.,Behl, M.,Lendlein, A. %D 2015 %J Advanced Functional Polymers for Medicine (AFPM) %N %P %T Biodegradable carrier/gene complexes to mediate proliferation and migration of human vascular endothelial cells %U %X %0 journal article %@ 1022-1360 %A Balk, M.,Behl, M.,Noechel, U.,Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 8-13 %R doi:10.1002/masy.201400043 %T Shape-Memory Hydrogels with Crystallizable Oligotetrahydrofuran Side Chains %U https://doi.org/10.1002/masy.201400043 1 %X Stimuli-sensitive materials, such as shape-memory polymers (SMP) have attracted tremendous interest in the field of biomedical applications and Regenerative Therapies. In case of implants intended for soft tissue, adequate elastic properties can be mimicked by water swollen hydrophilic polymer networks (i.e. hydrogels) and can be equipped with a shape-memory capability. Shape-memory hydrogels (SMHs) having body compatible transition temperatures (Ttrans) have not been reported so far. Here we explored, whether SMHs with Ttrans ≤ 37 °C could be created consisting of the hydrophilic poly(N-vinyl pyrrolidone) segment, the crosslinker oligo(ethylene glycol) dimethacrylate (OEGDMA, Mn = 370 g · mol−1), and grafted crystallizable oligotetrahydrofuran (OTHF, Mn = 7.100 g · mol−1, Tm = 31 °C) segments as switching domains. As function of the OTHF content (30–75 wt%), the hydrogels had a degree of swelling between 450 and 3200%, a Ttrans about 26 °C, and soft mechanical properties in the kPa range. Therefore, these SMHs might be interesting biomaterial candidates e.g. as smart implants. %0 journal article %@ 1022-1360 %A Saatchi, M.,Behl, M.,Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 100-107 %R doi:10.1002/masy.201400158 %T Double Layer Porous Structures by an Injection Molding/Particulate Leaching Approach %U https://doi.org/10.1002/masy.201400158 1 %X Scaffolds as a temporary substitute for the extracellular matrix should provide interconnected pores and often require a multilayer design to mimic the geometry and biomechanics of the target tissue. Here, it was explored whether bilayer porous structures can be obtained by a process free of organic solvents and how the individual layers contribute to the overall elastic properties. Porous layers were obtained from polyurethane (PU) blends with polyvinyl alcohol (PVA), which were immersed in water after sequential injection molding. Pore sizes in both layers ranged from 1 μm to 100 μm with an average of 22 ± 1 μm at a porosity of 50 ± 5% in combination with a high interconnectivity. The pore sizes were tailored by applying an annealing treatment, while the porosity was kept constant. Mechanical properties of the individual layers and the double layer constructs as determined by tensile tests suggested that the overall elasticity of the compact bilayer construct and porous bilayer construct was in agreement with the predicted overall elasticity according to the rule of mixtures. The porous bilayer model system will serve as a basis for determining structure-property relationships with respect to pore size, porosity as well as mechanical properties of individual layers and in this way enable a knowledge-based design of layered scaffolds. %0 journal article %@ 1022-1360 %A Baudis, S.,Lendlein, A.,Behl, M. %D 2014 %J Macromolecular Symposia %N 1 %P 105-111 %R doi:10.1002/masy.201400159 %T High-Throughput Synthesis as a Technology Platform for Copolymer Libraries %U https://doi.org/10.1002/masy.201400159 1 %X Quantitative structure-property relationships are of utmost importance for the rational design of materials. A systematic variation of one structure parameter in a series of polymers requires a large number of syntheses. Here combinatorial techniques are the method of choice. In this study high-throughput methods were applied for the synthesis and characterization of polymer libraries with stepwise changed composition to build up such material libraries. A high-throughput workflow was established, in which 112 different copolymerizations were performed. The polymers were characterized by means of NMR and FTIR (composition), GPC (number average molecular weight, inline imageand DSC (glass transition temperature, Tg). The gradually changed composition of the copolymers with number average molecular weights of around 150 kg ∙ mol-1 was confirmed and structure-property relationships between composition and Tgs ranging between 102 and 126 °C were proposed, rendering the polymer libraries now as a technology platform for further studies. %0 journal article %@ 1022-1352 %A Lv, J.,Hao, X.,Yang, J.,Feng, Y.,Behl, M.,Lendlein, A. %D 2014 %J Macromolecular Chemistry and Physics %N 24 %P 2463-2472 %R doi:10.1002/macp.201400345 %T Self-Assembly of Polyethylenimine-Modified Biodegradable Complex Micelles as Gene Transfer Vector for Proliferation of Endothelial Cells %U https://doi.org/10.1002/macp.201400345 24 %X Polyethylenimine (PEI) can perfectly condense with DNA and sufficiently transfer genes, but its high toxicity limits its application. Here, complex micelles are prepared as low-toxicity gene vectors by self-assembly of two block copolymers in aqueous solution. The complex micelles consist of a biodegradable poly(lactide-co-glycolide) (PLGA) core and a mixed poly(ethylene glycol) (PEG)/PEI shell. The ZNF580 gene plasmid (pEGFP-ZNF580), which has the ability of enhancing the proliferation of vascular endothelial cells, is encapsulated into the complex micelles. Using dynamic light scattering, the degradation behavior of the micelles is investigated in vitro. The hydrodynamic size and zeta potential of blank and DNA-loaded micelles are feasible to cellular uptake and gene transfection. 3-(4,5-Dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay shows that the cytotoxicity of the complex micelles is very low when the PEG/PEI ratio is 3/1. The DNA-loaded micelles are found to be able to enhance the proliferation of endothelial cells. %0 conference lecture %@ %A Baudis, S.,Lendlein, A.,Behl, M. %D 2014 %J 2014 MRS Fall Meeting & Exhibit, Symposium B %N %P %T Robot Assisted Synthesis and Characterization of Polyester-based Polyurethanes %U %X %0 journal article %@ 1022-1360 %A Kusmierczuk, M.,Noechel, U.,Baudis, S.,Behl, M.,Kratz, K.,Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 98-104 %R doi:10.1002/masy.201400150 %T Shape-Memory Polymer Networks Prepared from Star-Shaped Poly[(L-lactide)-co-glycolide] Precursors %U https://doi.org/10.1002/masy.201400150 1 %X Amorphous degradable copolymer networks such as poly[(L-lactide)-co-glycolide] (PLGA) are promising multifunctional polymers with tailorable degradation profiles and capable of a thermally-induced shape-memory effect. Currently, the shape-memory performance for covalently crosslinked networks based on linear PLGA dimethacrylate precursors (cPLGA) is limited. In this study we explored the shape-memory properties of cPLGA networks prepared from three-armed 2-isocyanatoethyl methacrylate functionalized precursors via photopolymerization. cPLGA exhibited excellent dual-shape properties characterized by an almost complete fixation of the temporary shape as well as an almost perfect recovery of the original shape. In the dry state cPLGA exhibited a switching temperature (Tsw) of 60 °C with a narrow recovery temperature interval of ΔTrec = 5 °C, while a significant lower Tsw of 40 °C with a ΔTrec = 15 °C was obtained when the polymer network was investigated in an aqueous environment. A concomitant decrease in the glass transition temperature could be observed in differential scanning calorimetry heating curves for copolymer networks after storage in aqueous buffer solution at 37 °C for 7 days, which can be attributed to the up-take of water molecules (1.5 wt%). The shape-memory properties achieved for cPLGA, in particular the shape recovery ratio and ΔTrec were superior to those of analogous polymer networks based on linear PLGA dimethacrylates. %0 conference lecture %@ %A Noechel, U.,Kratz, K.,Behl, M.,Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting & Exhibit, Symposium B %N %P %T Relation -between Nanostructural Changes and Macroscopic Effects during Reversible Temperature-Memory Effect under Stress-Free Conditions in Semicrystalline Polymer Networks %U %X %0 journal article %@ 1022-1360 %A Fang, L.,Yan, W.,Zierke, M.,Richau, K.,Behl, M.,Kratz, K.,Lendlein, A. %D 2014 %J Macromolecular Symposia %N 1 %P 83-90 %R doi:10.1002/masy.201400143 %T Crystallization and Phase Segregation of Multifunctional Multiblock Copolymers in Spin Coated Thin Films Altered by Diurethane Junction Units %U https://doi.org/10.1002/masy.201400143 1 %X A multiblock copolymer named PDC is composed of crystallizable oligo(p-dioxanone) (OPDO) and oligo(ε-caprolactone) (OCL) as hard and switching segments. PDC has been synthesized via connecting two oligomeric macrodiols using a diisocyanate linker such as 2,2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI) or 1,6-hexamethylene diisocyanate (HDI). In this work, the surface morphologies of spin coated thin films from two PDCs (PDC-HDI and PDC-TMDI) were investigated via in-situ atomic force microscopy (AFM) to examine how the diisocyanate linkers affect the balance between crystallization and phase segregation behavior. The results demonstrated that in PDC-HDI, the crystallization of poly(ε-caprolactone) (PCL) crystals provoked a “break out” from the phase segregated morphology. On contrary, the crystallization of PCL crystals in PDC-TMDI was strictly confined in the phase segregated morphology. %0 journal article %@ 1022-1360 %A Lendlein, A.,Behl, M.,Domb, A.J. %D 2014 %J Macromolecular Symposia %N 1 %P 7 %R doi:10.1002/masy.201470041 %T Preface %U https://doi.org/10.1002/masy.201470041 1 %X No abstract %0 journal article %@ 1022-1352 %A Baudis, S.,Behl, M.,Lendlein, A. %D 2014 %J Macromolecular Chemistry and Physics %N 24 %P 2399-2402 %R doi:10.1002/macp.201400561 %T Smart Polymers for Biomedical Applications %U https://doi.org/10.1002/macp.201400561 24 %X Smart materials have the ability to respond to changes in their environment by variations in their,molecular structure or in their physicochemical properties. Shape-memory and shape-changing,polymers are examples for this class of materials, whose capability to perform stimuli-induced,active movements has inspired engineers to develop heat-shrinkable packing materials, smart,textiles or morphing structures for aerospace vehicles. In the last 15 years these materials have,created significant interest in the field of biomedicine, e.g. in minimally invasive surgery for the,insertion of self-inflating bulky medical devices. The progress in material chemistry,,physicochemical characterization techniques, assessment of biomaterial interaction with cells,and tissues, and computer-assisted modelling motivates the exploration of knowledge-based,approaches for the design of active polymer systems. However, these active polymers are not,restricted to actively moving materials. They can offer a wide-spread spectrum of functions,,including controlled release, swellability, and degradability, that may be controlled by suitable,stimuli. The concepts for the design of smart polymers with the associated processes can be,categorized by the targeted device (e.g. coating, particles) and the nature of the function. Beside,shape-memory polymers[3] material systems of interest are stimuli-sensitive hydrogels[4] and,nanocarriers for the targeted administration of drugs or genes. %0 journal article %@ 1022-1352 %A Noechel, U.,Kumar, U.N.,Wang, K.,Kratz, K.,Behl, M.,Lendlein, A. %D 2014 %J Macromolecular Chemistry and Physics %N 24 %P 2446-2456 %R doi:10.1002/macp.201400445 %T Triple-Shape Effect with Adjustable Switching Temperatures in Crosslinked Poly[ethylene-co-(vinyl acetate)] %U https://doi.org/10.1002/macp.201400445 24 %X A triple-shape capability of copolymer networks enabling a variation of the two switching temperatures Tsws by purely physical functionalization is introduced. The polymer networks obtained by covalently crosslinking of poly[ethylene-co-(vinyl acetate)] exhibit a broad melting transition. The influence of the two deformation temperatures Tdeforms applied during programming of the triple-shape effect (TSE) on the two Tsws is explored. Interestingly, it turns out that the deformation geometry plays an important role in the realizability of this concept. Tensile deformations allow adjusting only one Tsw in the lower melting temperature range of 45 to 60 °C, whereas in bending tests, both Tsws can be varied. Finally, two independent TSEs associated to four different Tsws between 45 and 90 °C can be realized in the same specimen. Shape fixity and shape recovery ratios generally exceed 90%, demonstrating an excellent performance of the triple-shape function. %0 journal article %@ 1438-7492 %A Baudis, S.,Lendlein, A.,Behl, M. %D 2014 %J Macromolecular Materials and Engineering %N 11 %P 1292-1297 %R doi:10.1002/mame.201400073 %T High Throughput Characterization of Polymer Libraries by Diffuse Reflectance Infrared Spectroscopy %U https://doi.org/10.1002/mame.201400073 11 %X Diffuse reflectance FTIR (DRIFT) was established as a high throughput characterization method for classic copolymer systems. Four different methyl methacrylate-based polymer libraries with styrene, N-vinylpyrrolidone, 4-vinylpyridine, or 2-carboxyethyl acrylate as comonomers were synthesized using an automated/robotic synthesizer platform, and analyzed by 1H NMR and DRIFT. By multivariate data analysis both data sets were compared and correlations with R2 between 0.9373 and 0.9971 could be achieved. By this means high throughput screening of comonomer contents of these polymer libraries was enabled. %0 conference lecture %@ %A Heuchel, M.,Razzaq, M.,Kratz, K.,Behl, M.,Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting; Symp. B Multifunctional Polymeric and Hybrid Materials %N %P %T Modeling the heat transfer behavior of magnetosensitive shape-polymer nanocomposites with changing surface area to volume ratios %U %X %0 journal article %@ 2046-2069 %A Schmidt, C.,Behl, M.,Lendlein, A.,Beuermann, S. %D 2014 %J RSC Advances %N 66 %P 35099-35105 %R doi:10.1039/c4ra06815g %T Synthesis of high molecular weight polyglycolide in supercritical carbon dioxide %U https://doi.org/10.1039/c4ra06815g 66 %X Polyglycolide (PGA) is a biodegradable polymer with multiple applications in the medical sector. Here the synthesis of high molecular weight polyglycolide by ring-opening polymerization of diglycolide is reported. For the first time stabilizer free supercritical carbon dioxide (scCO2) was used as a reaction medium. scCO2 allowed for a reduction in reaction temperature compared to conventional processes. Together with the lowering of monomer concentration and consequently reduced heat generation compared to bulk reactions thermal decomposition of the product occurring already during polymerization is strongly reduced. The reaction temperatures and pressures were varied between 120 and 150 °C and 145 to 1400 bar. Tin(II) ethyl hexanoate and 1-dodecanol were used as catalyst and initiator, respectively. The highest number average molecular weight of 31200 g mol−1 was obtained in 5 hours from polymerization at 120 °C and 530 bar. In all cases the products were obtained as a dry white powder. Remarkably, independent of molecular weight the melting temperatures were always at (219 ± 2) °C. %0 journal article %@ 1042-7147 %A Lendlein, A.,Domb, A.J.,Baudis, S.,Behl, M. %D 2014 %J Polymers for Advanced Technologies %N 11 %P 1187-1188 %R doi:10.1002/pat.3377 %T From macromolecules to materials to systems %U https://doi.org/10.1002/pat.3377 11 %X No abstract %0 journal article %@ 0032-3861 %A Razzaq, M.Y.,Behl, M.,Noechel, U.,Lendlein, A. %D 2014 %J Polymer %N 23 %P 5953-5960 %R doi:10.1016/j.polymer.2014.07.025 %T Magnetically controlled shape-memory effects of hybrid nanocomposites from oligo(Omega-pentadecalactone) and covalently integrated magnetite nanoparticles %U https://doi.org/10.1016/j.polymer.2014.07.025 23 %X The covalent integration of inorganic nanoparticles in polymer matrices has gained significance for improving the structural properties of polymer-based materials. Here we report on the performance of poly(ω-pentadecalactone) networks with magnetite nanoparticles as netpoints in their magnetically-controlled shape-memory capability. Hybrid nanocomposites with magnetite nanoparticle content ranging from 5 to 11 wt% were prepared by reacting two types of oligo(ω-pentadecalactone) (OPDL) based precursors with terminal hydroxy groups, a three arm OPDL (3AOPDL, Mn = 6000 g mol−1) and an OPDL (Mn = 3300 g mol−1) coated magnetite nanoparticle (∅ = 10 nm), with a diisocyanate. Homogenous hybrid nanocomposites were obtained independent from the weight content of the OPDL decorated nanoparticles in the samples. At 100 °C (T > Tm-OPDL) the covalent integration of the nanoparticles increased the mechanical strength with increasing weight content whereby the elasticity remained almost constant. In magnetically-controlled one-way dual-shape experiments the shape fixity decreased from 95% to 90% but the shape recovery increased slightly from 95% to 97% when the nanoparticle content was increased. In magnetically-controlled reversible dual-shape experiments the nanoparticles had a restraining effect and the maximum shape-change of 65% for hybrid nanocomposites with 5 wt% magnetite nanoparticles was reduced to 36% when the particle content was increased to 11 wt%. These results show that the performance of hybrid nanocomposites can be tailored by nanoparticle content, however in terms of their applicability either mechanical strength or actuation capability should be focussed in the material selection. %0 conference lecture %@ %A Kratz, K.,Behl, M.,Nöchel, U.,Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting; Symp. B Multifunctional Polymeric and Hybrid Materials %N %P %T Crystallizable Polymer Networks Capable of Reversible Shape-Memory- Effects %U %X %0 conference lecture %@ %A Hao, X.,Lv, J.,Li, Q.,Fan, J.,Feng, Y.,Behl, M.,Lendlein, A. %D 2014 %J 3rd Symposium on Innovative Polymers for Controlled Delivery, SIPCD 2014 %N %P %T REDV-linked biodegradable polymeric micelles as the transfer vector of ZNF580 for the proliferation of endothelial cells %U %X %0 conference lecture (invited) %@ %A Lendlein, A.,Behl, M.,Neffe, A.T. %D 2014 %J 2nd International Conference on Bioinspired and Biobased Chemistry and Materials: Nature Inspires Chemical Engineers, NICE 2014 %N %P %T Design of Multifuncational Biomaterials by Chemical Integration of Functions %U %X %0 conference lecture %@ %A Behl, M.,Balk, M.,Nöchel, U.,Lendlein, A. %D 2014 %J MRS Fall Meeting 2014 %N %P %T Dual-Shape Hydrogels with Crystallizable; Oligomeric Switching Segments %U %X %0 conference lecture %@ %A Zhang, P.,Behl, M.,Lendlein, A. %D 2014 %J 6th Forum on New Materials: Symposium Smart Polymers for Biomedical Applications, CIMTEC 2014 %N %P %T Chemo-responsive Polymer Networks Containing Coordination Crosslinks and Covalent Netpoints %U %X %0 conference lecture (invited) %@ %A Behl, M.,Kratz, K.,Noechel, U.,Sauter, T.,Lendlein, A. %D 2014 %J 248th ACS National Meeting & Exposition %N %P %T Polymer networks capable of reversible shape-memory effects %U %X %0 conference poster %@ %A Balk, M.,Behl, M.,Noechel, U.,Lendlein, A. %D 2014 %J BCS Berliner Chemie Symposium / JCF Jungchemiker Forum %N %P %T Shape-Memory Hydrogels with Crystallizable Oligotetrahydrofuran Side Chains %U %X %0 conference lecture %@ %A Behl, M.,Kratz, K.,Noechel, U.,Lendlein, A. %D 2014 %J 6th Forum on New Materials: Symposium Smart Polymers for Biomedical Applications, CIMTEC 2014 %N %P %T Reversible Actuation of Polymer Networks by Directed Crystallization %U %X %0 conference lecture %@ %A Balk, M.,Behl, M.,Noechel, U.,Lendlein, A. %D 2014 %J 6th Forum on New Materials: Symposium Smart Polymers for Biomedical Applications, CIMTEC 2014 %N %P %T Oligotetrahydrofurane Based Shape-memory Hydrogels %U %X %0 conference lecture (invited) %@ %A Behl, M.,Lendlein, A. %D 2014 %J Hangzhou International Polymer Forum, HIPF %N %P %T Knowledge-based Design of Actively Moving Polymer Networks %U %X %0 conference lecture %@ %A Braune, S.,Dietze, S.,Roch, T.,Krueger, A.,Baudis, S.,Behl, M.,Kratz, K.,Jung, F.,Lendlein, A. %D 2014 %J 6th Forum on New Materials: Symposium Smart Polymers for Biomedical Applications, CIMTEC 2014 %N %P %T Bicompatibility of a Degradable Poly[(L-lactide)-coglycolide] Network %U %X %0 conference lecture (invited) %@ %A Behl, M.,Razzaq, M.,Kratz, K.,Lendlein, A. %D 2014 %J SPIE BiOS 2014 %N %P %T Magnetically triggered active Hybrid- Nanocomposites %U %X %0 conference lecture (invited) %@ %A Kratz, K.,Behl, M.,Noechel, U.,Sauter, T.,Lendlein, A. %D 2014 %J Polymermischungen 2014, Polymerblends und Nanocomposites %N %P %T Reversible Shape- Memory- Effects in Polymer Networks %U %X %0 conference lecture %@ %A Razzaq, M.,Behl, M.,Nöchel, U.,Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting; Symp. B Multifunctional Polymeric and Hybrid Materials %N %P %T Magneto-sensitive hybrid nanocomposites based on oligo(omega-pentadecalactone) and covalently integrated magnetic nanoparticles %U %X %0 conference lecture %@ %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting & Exhibit, Symposium B %N %P %T Thermally Controlled Shape-Memory Investigations of Nanocomposites Based on Oligo(ω-pentadecalactone) and Magnetic Nanoparticles Acting as Crosslinks %U %X %0 conference lecture %@ %A Heuchel, M.,Al-Qaisi, L.,Kratz, K.,Noechel, U.,Behl, M.,Lendlein, A. %D 2014 %J 2014 MRS Fall Meeting & Exhibit %N %P %T Thermomechanical Characterization of a Series of Crosslinked Poly[ethylene-co-(vinyl acetate)] (PEVA) Copolymers %U %X %0 conference poster %@ %A Baudis, S.,Lendlein, A.,Behl, M. %D 2014 %J 2014 MRS Fall Meeting & Exhibit %N %P %T Robotic Synthesis of Polyester- and Depsipeptide- based Polyurethanes %U %X %0 journal article %@ 1022-1360 %A Saatchi, M.,Behl, M.,Lendlein, A. %D 2013 %J Macromolecular Symposia %N 1 %P 33-39 %R doi:10.1002/masy.201300151 %T Manufacturing and Characterization of Controlled Foaming of Single Layers in Bilayer Constructs Differing in Pore Morphology %U https://doi.org/10.1002/masy.201300151 1 %X Bilayer porous constructs from degradable polymers are considered as scaffold materials with beneficial elastic properties for cell culture application in tissue engineering. Here, we explored whether such bilayer constructs, in which only one layer was porous while the other layer enhanced the compressive mechanical properties, could be created by specific foaming of one layer with supercritical carbon dioxide (scCO2). The bilayer constructs of a poly(L-lactide) (PLLA) and a poly(ϵ-caprolactone) (PCL) layer were prepared by sequential injection molding and subsequent specific foaming with scCO2. Foaming conditions of T = 45 °C and P = 100 bar resulted in the formation of a porous PCL layer and a non-porous PLLA layer. When the time intervals of the foaming process were increased the pore size was increased and the shape of the pores was changed from a circular to an unidirectional lamellar shape, which reduced the compressive elastic modulus of the porous PCL layer. Furthermore, the foaming process increased the adhesion force between the PLLA and PCL layers, which was attributed to a higher degree of diffusion of molten PCL into the PLLA layer. In summary, it was demonstrated that scCO2 foaming is a suitable method for the creation of layered scaffolds with only one foamed layer, in which the compressive elastic modulus and pore morphology of single porous layers can be controlled by the time interval of scCO2 process. %0 journal article %@ 1022-1352 %A Julich-Gruner, K.K.,Loewenberg, C.,Neffe, A.T.,Behl, M.,Lendlein, A. %D 2013 %J Macromolecular Chemistry and Physics %N 5 %P 527-536 %R doi:10.1002/macp.201200607 %T Recent Trends in the Chemistry of Shape-Memory Polymers %U https://doi.org/10.1002/macp.201200607 5 %X Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of performing complex movements on demand, which makes them interesting candidates for various applications, for example, in biomedicine or aerospace. This trend article highlights current approaches in the chemistry of SMPs, such as tailored segment chemistry to integrate additional functions and novel synthetic routes toward permanent and temporary netpoints. Multiphase polymer networks and multimaterial systems illustrate that SMPs can be constructed as a modular system of different building blocks and netpoints. Future developments are aiming at multifunctional and multistimuli-sensitive SMPs. %0 journal article %@ 2280-8000 %A Friess, F.,Wischke, C.,Behl, M.,Lendlein, A. %D 2013 %J Journal of Applied Biomaterials & Functional Materials %N 3 %P 273-279 %R doi:10.5301/JABFM.2012.10372 %T Oligo(Epsilon-caprolactone)-based polymer networks prepared by photocrosslinking in solution %U https://doi.org/10.5301/JABFM.2012.10372 3 %X Purpose: Polymer networks with adjustable properties prepared from endgroup-functionalized oligoesters by UV-crosslinking in melt have evolved into versatile multifunctional biomaterials. In addition to the molecular weight or architecture of precursors, the reaction conditions for crosslinking are pivotal for the polymer network properties. Crosslinking of precursors in solution may facilitate low-temperature processes and are compared here to networks synthesized in melt.
Methods: Oligo(ε-caprolactone)-(z)methacrylate (oCL-(z)IEMA) precursors with a linear (z = di) or a four-armed star-shaped (z = tetra) architecture were crosslinked by radical polymerization in melt or in solution with UV irradiation. The thermal, mechanical, and swelling properties of the polymer networks obtained were characterized.
Results: Crosslinking in solution resulted in materials with lower Young’s moduli (E), lower maximum stress (σmax), and higher elongation at break (εB) as determined at 70 °C. Polymer networks from 8 kDa star-shaped precursors exhibited poor elasticity when synthesized in the melt, but can be established as stretchable materials with a semi-crystalline morphology, a high gel- content, and a high elongation at break when prepared in solution.
Conclusions: The crosslinking condition of methacrylate functionalized precursors significantly affected network properties. For some types of precursors such as star-shaped telechelics, synthesis in solution provided semi-crystalline elastic materials that were not accessible from crosslinking in melt. %0 journal article %@ 0957-4530 %A Feng, Y.,Zhao, H.,Behl, M.,Lendlein, A.,Guo, J.,Yang, D. %D 2013 %J Journal of Materials Science: Materials in Medicine %N 1 %P 61-70 %R doi:10.1007/s10856-012-4685-4 %T Grafting of poly(ethylene glycol) monoacrylates on polycarbonateurethane by UV initiated polymerization for improving hemocompatibility %U https://doi.org/10.1007/s10856-012-4685-4 1 %X Poly(ethylene glycol) monoacrylates (PEGMAs) with a molecular weight between 400 and 1,000 g mol−1 were grafted by ultraviolet initiated photopolymerization on the surface of polycarbonateurethane (PCU) for increasing its hydrophilicity and improving its hemocompatibility. The surface-grafted PCU films were characterized by Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle, scanning electron microscopy (SEM) and atomic force microscopy measurements. The surface properties of the modified films were studied in dry and wetted state. Blood compatibility of the surfaces was evaluated by platelet adhesion tests and adhered platelets were determined by SEM. The results showed that the hydrophilicity of the films had been increased significantly by grafting PEGMAs, and platelets adhesion onto the film surface was obviously suppressed. Furthermore, the molecular weight of PEGMAs had a great effect on the hydrophilicity and hemocompatibility of the PCU films after surface modification and increased with increasing molecular weight of PEGMAs. %0 journal article %@ 1616-5187 %A Yang, J.,Lv, J.,Behl, M.,Lendlein, A.,Yang, D.,Zhang, L.,Shi, C.,Guo, J.,Feng, Y. %D 2013 %J Macromolecular Bioscience %N 12 %P 1681-1688 %R doi:10.1002/mabi.201300264 %T Functionalization of Polycarbonate Surfaces by Grafting PEG and Zwitterionic Polymers with a Multicomb Structure %U https://doi.org/10.1002/mabi.201300264 12 %X The hemocompatibility of polycarbonateurethane (PCU) surfaces is improved by decoration with poly(poly(ethylene glycol) methacrylate) (poly(PEGMA)) and zwitterionic poly(3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate) (poly(DMAPS)) blocks providing a novel multicomb structure obtained by application of surface-initiated atom transfer radical polymerization (s-ATRP) conditions. The PCU-poly(PEGMA-g-DMAPS) surface shows high hydrophilicity with a low contact angle of 20.6 ± 1.8°, while PCU-poly(PEGMA-b-DMAPS) surface exhibitsed a contact angle of 30.5 ± 2.6°. Furthermore, PCU-poly(PEGMA-g-DMAPS) surface shows very low platelet adsorption indicating that multicomb structure modified PCUs are preferred candidate materials for blood-contacting materials. %0 conference lecture %@ %A Behl, M.,Lendlein, A. %D 2013 %J Helmholtz Graduate School for Macromolecular Bioscience Summer School 2013 %N %P %T Welcome to HZG Campus Teltow, Institute for Biomaterial Science %U %X %0 journal article %@ 1742-5247 %A Wischke, C.,Behl, M.,Lendlein, A. %D 2013 %J Expert Opinion on Drug Delivery %N 9 %P 1193-1205 %R doi:10.1517/17425247.2013.797406 %T Drug-releasing shape-memory polymers – The role of morphology, processing effects, and matrix degradation %U https://doi.org/10.1517/17425247.2013.797406 9 %X Introduction: Shape-memory polymers (SMPs) have gained interest for temporary drug-release systems that should be anchored in the body by self-sufficient active movements of the polymeric matrix.,Areas covered: Based on the so far published scientific literature, this review highlights three aspects that require particular attention when combining SMPs with drug molecules: i) the defined polymer morphology as required for the shape-memory function, ii) the strong effects that processing conditions such as drug-loading methodologies can have on the drug-release pattern from SMPs, and iii) the independent control of drug release and degradation by their timely separation.,Expert opinion: The combination of SMPs with a drug-release functionality leads to multifunctional carriers that are an interesting technology for pharmaceutical sciences and can be further expanded by new materials such as thermoplastic SMPs or temperature-memory polymers. Experimental studies should include relevant molecules as (model) drugs and provide a thermomechanical characterization also in an aqueous environment, report on the potential effect of drug type and loading levels on the shape-memory functionality, and explore the potential correlation of polymer degradation and drug release. %0 conference poster %@ %A Krueger, A.,Scharnagl, N.,Trescher, K.,Zierke, M.,kratz, K.,Behl, M.,Jung, F.,Lendlein, A. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %N %P %T Behaviour of fibroblasts on water born acrylonitrile based copolymers with varying hydrophilicities %U %X %0 conference poster %@ %A Schmidt, C.,Behl, M.,Lendlein, A.,Beuermann, S. %D 2013 %J 2013 MRS Spring Meeting and Exhibit %N %P %T Supercritical Carbon Dioxide as Reaction Medium for the Synthesis of the Biodegradable Polymer Polyglycolide %U %X %0 journal article %@ 1946-4274 %A Roch, T.,Behl, M.,Zierke, M.,Pierce, B.F.,Kratz, K.,Weigel, T.,Ma, N.,Lendlein, A. %D 2013 %J MRS Online Proceedings Library %N %P 21-26 %R doi:10.1557/opl.2013.830 %T The influence of the co-monomer ratio of poly[acrylonitrile-co-(N-vinylpyrrolidone)]s on primary human monocyte-derived dendritic cells %U https://doi.org/10.1557/opl.2013.830 %X A major goal in the field of regenerative medicine is to improve our understanding of how biomaterial properties affect cells of the immune system. Systematic variation of defined chemical properties could help to understand which factors determine and modulate cellular responses. A series of copolymers poly[acrylonitrile-co-(N-vinylpyrrolidone)]s (P(AN-co-NVP)) served as model system, in which increasing hydrophilicity was adjusted by increasing the content related to the NVP based repeating units (nNVP) (0, 4.6, 11.8, 22.3, and 29.4 mol%). The influence of increasing nNVP contents on cellular response of human primary monocyte derived dendritic cells (DC), which play a key role in the initiation of immune responses, was investigated. It was shown using the LAL-Test as well as a macrophage-based assay, that the materials were free of endotoxins and other microbial contaminations, which could otherwise bias the readout of the DC experiments. The increasing nNVP content led to a slightly increased cell death of DC, whereas the activation status of DC was not systematically altered by the different P(AN-co-NVP)s as demonstrated by the expression of co-stimulatory molecule and cytokine secretion. Similarly, under inflammatory conditions mimicked by the addition of lipopolysaccharides (LPS), neither the expression of co-stimulatory molecules nor the release of cytokines was influenced by the different copolymers. Conclusively, our data showed that this class of copolymers does not substantially influence the viability and the activation status of DC. %0 conference lecture %@ %A Behl, M.,Razzaq, M.,Lendlein, A. %D 2013 %J 2013 MRS Spring Meeting and Exhibit %N %P %T Nanocomposites of Magnetic Nanoparticles in Crystallizable Matrices as Platform Technology for Actively Moving Polymers %U %X %0 journal article %@ 1744-683X %A Zhao, Q.,Behl, M.,Lendlein, A. %D 2013 %J Soft Matter %N 6 %P 1744-1755 %R doi:10.1039/c2sm27077c %T Shape-memory polymers with multiple transitions: Complex actively moving polymers %U https://doi.org/10.1039/c2sm27077c 6 %X Shape-memory polymers (SMPs) are able to perform shape transitions in a pre-defined pathway in response to suitable external stimuli such as heat, magnetism, electricity, moisture, or light. Most of the SMPs are dual-shape materials, which enable a single shape transition from a temporary to a permanent shape. Recently, triple-shape polymers (TSPs), which are capable of accomplishing two shape transitions, as well as multi-shape polymers with shape changes have been introduced including temperature-memory polymers (TMPs) with tunable multiple shape transitions. Different concepts for obtaining multi-shape polymers are introduced and the sophisticated structural design concepts in combination with tailored shape-memory creation processes (SMCPs) are explained. Future opportunities emerge in alternative actuation methods and exploration of potential applications. %0 conference lecture %@ %A Kratz, K.,Behl, M.,Noechel, U.,Sauter, T.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Polymer Networks Exhibiting a Reversible Temperature-Memory Effect %U %X %0 conference lecture %@ %A Behl, M.,Kratz, K.,Noechel, U.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Reversible, Bidirectional Shape-memory Polymers by Directed Crystallization %U %X %0 conference poster %@ %A Fang, L.,Yan, W.,Noechel, U.,Zierke, M.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J 2013 MRS Spring Meeting and Exhibit, Symposium MM – Advanced Materials for Biological and Biomedical Applications %N %P %T Influence of Coupling Agent on the Morphology of Multifunctional, Degradable Shape-Memory Polymers %U %X %0 conference poster %@ %A Tartivel, L.,Behl, M.,Schroeter, M.,Lendlein, A. %D 2013 %J 2013 MRS Spring Meeting and Exhibit, Symposium MM – Advanced Materials for Biological and Biomedical Applications %N %P %T ABA triblock copolymer based hydrogels with thermo-sensitivity for biomedical applications %U %X %0 journal article %@ 0014-3057 %A Noechel, U.,Reddy, C.S.,Uttamchand, N.K.,Kratz, K.,Behl, M.,Lendlein, A. %D 2013 %J European Polymer Journal %N 9 %P 2457-2466 %R doi:10.1016/j.eurpolymj.2013.01.022 %T Shape-memory properties of hydrogels having a poly(Epsilon-caprolactone) crosslinker and switching segment in an aqueous environment %U https://doi.org/10.1016/j.eurpolymj.2013.01.022 9 %X Multiphase copolymer networks are of great relevance as their thermal and mechanical as well as shape-memory properties can be adjusted by the variation of the composition and crosslink density. In this context recently grafted copolymer networks (named CLEG), prepared by thermal free-radical polymerization with different ratios of the hydrophobic telechelic crosslinker poly(ε-caprolactone) diisocyanoethyl methacrylate (PCLDIMA, Tm,PCL = 55 °C) and hydrophilic poly(ethylene glycol) monomethyl ether monomethacrylate (PEGMA, Tm,PEG = 38 °C) as co-monomer, were introduced, which additionally allow the alteration of the overall elastic properties via controlled water uptake.,Here we study the thermomechanical properties as well as the shape-memory behavior of a series of CLEG copolymer networks in an aqueous environment. The mechanical properties of the networks at 25 °C in aqueous environment were found to increase from 4 MPa to 77 MPa with increasing crosslink density. The shape-memory properties of the copolymer networks were examined in an aqueous environment by both bending as well as uniaxial elongation experiments. Excellent dual-shape properties with high shape fixity ratios around Rf = 79–100% and shape recovery ratios in the range of Rr = 59% to Rr = 100% were obtained for copolymers with a PCLDIMA weight fraction ⩾50 wt% in the starting composition. The swelling of CLEG in H2O resulted in a reduction of the switching temperature. Furthermore the structural changes during programming of CLEG were assessed in situ by small and wide angle X-ray scattering (SAXS, WAXS) experiments, which confirmed that the overall degree of crystallinity as well as the orientation of the crystalline domains controlled the dual-shape performance. We have found that an appropriate switching segment should result in a degree of crystallinity higher than 10–20% to enable high strain fixity ratios. Furthermore, hydrogels having dual shape-memory capability could be created by using semi-crystalline crosslinker simultaneously acting as the switching segment. %0 conference lecture (invited) %@ %A Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J Soft Control - Switching Surface Properties with Stimulus Responsive Polymers at Interfaces %N %P %T Shape-Memory Polymers – From One Way Effects to Programmable Actuators %U %X %0 conference poster %@ %A Dietze, S.,Braune, S.,Krueger, A.,Baudis, S.,Behl, M.,Kratz, K.,Jung, F.,Lendlein, A. %D 2013 %J 32. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %N %P %T Hemocompatibility of degradable poly[(rac-lactide)-co-glycolide] polymer network %U %X %0 journal article %@ 0142-9612 %A Sharifi, S.,van Kooten, T.G.,Kranenburg, H.J.C.,Meij, B.P.,Behl, M.,Lendlein, A.,Grijpma, D.W. %D 2013 %J Biomaterials %N 33 %P 8105-8113 %R doi:10.1016/j.biomaterials.2013.07.061 %T An annulus fibrosus closure device based on a biodegradable shape-memory polymer network %U https://doi.org/10.1016/j.biomaterials.2013.07.061 33 %X Injuries to the intervertebral disc caused by degeneration or trauma often lead to tearing of the annulus fibrosus (AF) and extrusion of the nucleus pulposus (NP). This can compress nerves and cause lower back pain. In this study, the characteristics of poly(d,l-lactide-co-trimethylene carbonate) networks with shape-memory properties have been evaluated in order to prepare biodegradable AF closure devices that can be implanted minimally invasively. Four different macromers with (d,l-lactide) to trimethylene carbonate (DLLA:TMC) molar ratios of 80:20, 70:30, 60:40 and 40:60 with terminal methacrylate groups and molecular weights of approximately 30 kg mol−1 were used to prepare the networks by photo-crosslinking. The mechanical properties of the samples and their shape-memory properties were determined at temperatures of 0 °C and 40 °C by tensile tests- and cyclic, thermo-mechanical measurements. At 40 °C all networks showed rubber-like behavior and were flexible with elastic modulus values of 1.7–2.5 MPa, which is in the range of the modulus values of human annulus fibrosus tissue. The shape-memory characteristics of the networks were excellent with values of the shape-fixity and the shape-recovery ratio higher than 98 and 95%, respectively. The switching temperatures were between 10 and 39 °C. In vitro culture and qualitative immunocytochemistry of human annulus fibrosus cells on shape-memory films with DLLA:TMC molar ratios of 60:40 showed very good ability of the networks to support the adhesion and growth of human AF cells. When the polymer network films were coated by adsorption of fibronectin, cell attachment, cell spreading, and extracellular matrix production was further improved. Annulus fibrosus closure devices were prepared from these AF cell-compatible materials by photo-polymerizing the reactive precursors in a mold. Insertion of the multifunctional implant in the disc of a cadaveric canine spine showed that these shape-memory devices could be implanted through a small slit and to some extent deploy self-sufficiently within the disc cavity. %0 conference poster %@ %A Behl, M.,Kratz, K.,Noechel, U.,Zotzmann, J.,Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %N %P %T Directed Crystallization turns Poly(Omega-pentadecalactone)-based Multiphase Polymer Networks into Active Polymers %U %X %0 conference poster %@ %A Feng, Y.,Zhang, L.,Behl, M.,Lendlein, A.,Shi, C.,Lv, J.,Yang, J. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %N %P %T Amphiphilic depsipeptide/PEG block copolymer Microspheres and release of doxorubicin %U %X %0 conference object %@ %A Lendlein, A.,Razzaq, M.Y.,Kratz, K.,Behl, M. %D 2013 %J Abstracts of Papers of the American Chemical Society, 245th National Spring Meeting of the American-Chemical-Society %N %P 164-PMSE %T Magnetically triggered memory-effects of active nanocomposites %U %X %0 conference poster %@ %A Saatchi, M.,Behl, M.,Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %N %P %T Preparation and characterization of selective porous layer in multilayer structure %U %X %0 journal article %@ 0027-8424 %A Behl, M.,Kratz, K.,Noechel, U.,Sauter, T.,Lendlein, A. %D 2013 %J Proceedings of the National Academy of Sciences of the United States of America: PNAS %N 31 %P 12555-12559 %R doi:10.1073/pnas.1301895110 %T Temperature-memory polymer actuators %U https://doi.org/10.1073/pnas.1301895110 31 %X Reading out the temperature-memory of polymers, which is their ability to remember the temperature where they were deformed recently, is thus far unavoidably linked to erasing this memory effect. Here temperature-memory polymer actuators (TMPAs) based on cross-linked copolymer networks exhibiting a broad melting temperature range (ΔTm) are presented, which are capable of a long-term temperature-memory enabling more than 250 cyclic thermally controlled actuations with almost constant performance. The characteristic actuation temperatures Tacts of TMPAs can be adjusted by a purely physical process, guiding a directed crystallization in a temperature range of up to 40 °C by variation of the parameter Tsep in a nearly linear correlation. The temperature Tsep divides ΔTm into an upper Tm range (T > Tsep) forming a reshapeable actuation geometry that determines the skeleton and a lower Tm range (T < Tsep) that enables the temperature-controlled bidirectional actuation by crystallization-induced elongation and melting-induced contraction. The macroscopic bidirectional shape changes in TMPAs could be correlated with changes in the nanostructure of the crystallizable domains as a result of in situ X-ray investigations. Potential applications of TMPAs include heat engines with adjustable rotation rate and active building facades with self-regulating sun protectors. %0 journal article %@ 0935-9648 %A Razzaq, M.Y.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J Advanced Materials %N 40 %P 5730-5733 %R doi:10.1002/adma.201302485 %T Multifunctional Hybrid Nanocomposites with Magnetically Controlled Reversible Shape–Memory Effect %U https://doi.org/10.1002/adma.201302485 40 %X Magneto-sensitivity and a thermo-sensitive reversible shape–memory effect have been successfully integrated into a hybrid nanocomposite, resulting in a magnetically controlled actuator. The complex requirements for gaining this multifunctionality are fulfilled by combining netpoints on the molecular and nano level in a polyesterurethane network prepared from hydroxyl group decorated magnetic nanoparticles, crystallizable star-shaped poly(ω-pentadecalactone) precursors, and a diisocyanate. %0 conference lecture (invited) %@ %A Behl, M.,Lendlein, A. %D 2013 %J International Workshop on Biodegradable Polymers in Medicine %N %P %T Oligodepsipeptide- and Oligoester-based Copolymers %U %X %0 conference poster %@ %A Balk, M.,Behl, M.,Noechel, U.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Shape-Memory Hydrogels with Crystallizable Oligotetrahydrofurane Side Chains %U %X %0 journal article %@ 0935-9648 %A Razzaq, M.Y.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J Advanced Materials %N 38 %P 5514-5518 %R doi:10.1002/adma.201301521 %T Triple-Shape Effect in Polymer-Based Composites by Cleverly Matching Geometry of Active Component with Heating Method %U https://doi.org/10.1002/adma.201301521 38 %X A triple-shape effect is created for a segmented device consisting of an active component encapsulated in a highly flexible polymer network. Segments with the same composition but different interface areas can be recovered independently either at specific field strengths (Hsw) during inductive heating, at a specific time during environmentally heating, or at different airflow during inductive heating at constant H. Herein the type of heating method regulates the sequence order. %0 journal article %@ 0935-9648 %A Behl, M.,Kratz, K.,Zotzmann, J.,Nöchel, U.,Lendlein, A. %D 2013 %J Advanced Materials %N 32 %P 4466-4469 %R doi:10.1002/adma.201300880 %T Reversible Bidirectional Shape-Memory Polymers %U https://doi.org/10.1002/adma.201300880 32 %X Free-standing copolymer network samples with two types of crystallizable domains are capable of a fully reversible bidirectional shape-memory effect. One set of crystallizable domains determines the shape-shifting geometry while the other provides the thermally controlled actuation capability. %0 journal article %@ 1946-4274 %A Behl, M.,Razzaq, M.Y.,Lendlein, A. %D 2013 %J MRS Online Proceedings Library %N %P 129-134 %R doi:10.1557/opl.2013.1060 %T Tailoring the recovery force in magnetic shape-memory nanocomposites %U https://doi.org/10.1557/opl.2013.1060 %X Composites from magnetic nanoparticles in a shape-memory polymer (SMP) matrix allow a remote actuation of the shape-memory effect by exposure to alternating magnetic fields. At the same time the incorporation of MNP may affect the thermal properties and the structural functions of the SMP.,Here, we explored the adjustability of the recovery force as an important structural function in magnetic shape-memory nanocomposites (mSMC) by variation of the programing temperature (Tprog) and nanoparticle weight content. The nanocomposites were prepared by coextrusion of silica coated magnetite nanoparticles (mNP) with an amorphous polyether urethane (PEU) matrix. In tensile tests in whichTprog was varied between 25 and 70 °C and the particle content from 0 to 10 wt% it was found that the Young’s moduli (E) decreased with temperature and particle content. Cyclic, thermomechanical experiments with a recovery module under strain-control conditions were performed to monitor the effect of mNP andTprog on the recovery force of the composites. During the strain-control recovery the maximum stress (σm, r) at a characteristic temperature (Tσ, max) was recorded. By increasing the mNP content from 0 to 10 wt% in composites, σm, r of 1.9 MPa was decreased to 1.25 MPa at aTprog = 25 °C. A similar decrease inσm, r for nanocomposites with different mNP content could be observed whenTprog was increased from 25 °C to 70 °C. It can be concluded that the lower the deformation temperature and the particle content the higher is the recovery force. %0 conference poster %@ %A Zhang, P.,Behl, M.,Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %N %P %T Chemo-responsive Polymer Networks Based on Rhodium Coordination Bonds %U %X %0 conference lecture (invited) %@ %A Behl, M.,Lendlein, A. %D 2013 %J Symposium in Honor of the 60th Birthday of Prof. Rudolf Zentel %N %P %T From Dual-Shape Polymers to Temperature-Memory Polymer Actuators %U %X %0 conference poster %@ %A Fang, L.,Yan, W.,Zierke, M.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J Advanced Functional Polymers for Medicine, 533th WE-Heraeus-Seminar %N %P %T Morphology of Spin-coated Films from Copolyetheresterurethanes Containing Different Aliphatic Diisocyanate Linkers %U %X %0 conference lecture %@ %A Behl, M.,Lendlein, A. %D 2013 %J Nanomaterials for Biomedical Applications, 3rd Sino-German Symposium 2013 %N %P %T Stimuli-sensitive Biomaterials %U %X %0 conference lecture (invited) %@ %A Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J International Workshop on Biodegradable Polymers in Medicine %N %P %T Shape-Memory Polymers %U %X %0 journal article %@ 1946-4274 %A Wang, L.,Nöchel, U.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J MRS Online Proceedings Library %N %P 123-128 %R doi:10.1557/opl.2013.799 %T Comparison of memory effects in multiblock copolymers and covalently crosslinked multiphase polymer networks composed of the same types of oligoester segments and urethane linker %U https://doi.org/10.1557/opl.2013.799 %X Phase-segregated multiblock copolymers (MBC) as well as covalently crosslinked multiphase polymer networks, which are composed of crystallizable oligo(ε-caprolactone) (OCL) and oligo(ω-pentadecalactone) (OPDL) segments have been recently introduced as degradable polymer systems exhibiting various memory effects. Both types of copolyesterurethane networks can be synthesized via co-condensation of the respective hydroxytelechelic oligomers and 2, 2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI) as aliphatic linker.,In this work the dual-shape properties as well as the temperature-memory capability of thermoplastics and covalently crosslinked copolyesterurethanes containing OCL and OPDL domains are explored. Both copolyesterurethane networks exhibited excellent dual-shape properties with high shape fixity ratiosRf ≥ 93% and shape recovery ratios in the range of 92% to 100% determined in the 2nd and 3rd test cycle, whereby the dual-shape performance was substantially improved when covalent crosslinks are present in the copolymer.,A pronounced temperature-memory effect was achieved for thermoplastic as well as crosslinked copolyesterurethanes. Hereby, the switching temperatureTsw could be adjusted via the variation of the applied deformation temperatureTdeform in the range from 32 °C to 53 °C for MBC and in the range from 29 °C to 78 °C for multiphase polymer networks. %0 conference poster %@ %A Roch, T.,Behl, M.,Zierke, M.,Pierce, B.F.,Weigel, T.,Ma, N.,Kratz, K.,Lendlein, A. %D 2013 %J 2013 MRS Spring Meeting and Exhibit, Symposium NN – Multifunctional Biomaterials %N %P %T The influence of the co-monomer ratio of poly[acrylonitrile-co-(N-vinylpyrrolidone)]s on primary human monocyte-derived dendritic cells %U %X %0 journal article %@ 1022-1352 %A Schroeter, M.,Behl, M.,Kaiser, C.,Lendlein, A. %D 2013 %J Macromolecular Chemistry and Physics %N 11 %P 1215-1224 %R doi:10.1002/macp.201300059 %T Synthesis and Properties of Poly(p-phenylene ethynylene)s with Oxidation- and Reduction-Sensitive Moieties %U https://doi.org/10.1002/macp.201300059 11 %X The synthesis of redox-sensitive poly(p-phenylene ethynylene)s (rsPPEs) bearing protected quinones in their backbone by the Sonogashira coupling reaction is described. The rsPPEs show excellent solubility in toluene, tetrahydrofurane, and chloroform. Cleavage of the protection group of the incorporated quinone moieties enables main-chain conductive polymers having redox-sensitive properties to be produced. These redox-sensitive switches can be reduced and oxidized in solution, as well as in the solid state, accompanied by a change of the photoluminescence values. The processes occurring during oxidation and reduction are analyzed by UV–vis and photoluminescence spectroscopy and lead to a decrease of intensity of 80% during oxidation. Such multifunctional polymers may be useful for redox-potential changing stimuli in biological systems. %0 conference lecture %@ %A Razzaq, M.,Behl, M.,Lendlein, A. %D 2013 %J Helmholtz Graduate School for Macromolecular Bioscience, Summer School 2013 %N %P %T Multifunctional Hybrid Nanocomposites With Magnetically Controlled Reversible Shape-Memory Effect %U %X %0 conference lecture (invited) %@ %A Lendlein, A.,Razzaq, M.Y.,Kratz, K.,Behl, M. %D 2013 %J 245th National Spring Meeting of the American-Chemical-Society %N %P %T Magnetically triggered memory-effects of active nanocomposites %U %X %0 journal article %@ 1946-4274 %A Fang, L.,Yan, W.,Noechel, U.,Zierke, M.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J MRS Online Proceedings Library %N %P 57-64 %R doi:10.1557/opl.2013.805 %T Influence of Coupling Agent on the Morphology of Multifunctional, Degradable Shape-Memory Polymers %U https://doi.org/10.1557/opl.2013.805 %X Multifunctional polymer-based biomaterials, which combine degradability and shapememory capability, are promising candidate materials for biomedical implants. An example is a degradable multiblock copolymer (PDC), composed of poly(p-dioxanone) (PPDO) as hard and poly(ε-caprolactone) (PCL) as switching segments. PDC exhibits a unique linear mass loss during hydrolytic degradation, which can be tailored by the PPDO to PCL weight ratio, as well as an excellent thermally induced dual-shape effect. PDC can be synthesized by co-condensation of two oligomeric macrodiols (PCL-diol and PPDO-diol) using aliphatic diisocyanates as coupling agent. Here, we investigated whether different morphologies could be obtained for PDCs synthesized from identical oligomeric macrodiols (PCL-diol with M n = 2000 g·mol-1 and PPDO-diol with M n = 5300-5500 g·mol-1) with 2, 2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI) and 1, 6-hexamethylene diisocyanate (HDI), respectively. More specifically, atomic force microscopy (AFM) was utilized for an investigation of the surface morphologies in solution casted PDC thin films in the temperature range from 20 °C to 60 °C. The results obtained in differential scanning calorimetry (DSC) and AFM demonstrated that different morphologies were obtained when TMDI (PDC-TMDI) or HDI (PDC-HDI) were used as linker. PCL related crystals in PDC-HDI were more heterogeneous and less ordered than those in PDCTMDI, while HDI resulted in a larger degree of crystallinity than TMDI. This research provides some new suggestions for choosing a suitable coupling agent to tailor the required morphologies and properties of SMPs with crystallizable switching segments. %0 journal article %@ 1946-4274 %A Tartivel, L.,Behl, M.,Schroeter, M.,Lendlein, A. %D 2013 %J MRS Online Proceedings Library %N %P 135-140 %R doi:10.1557/opl.2013.840 %T ABA triblock copolymer based hydrogels with thermo-sensitivity for biomedical applications %U https://doi.org/10.1557/opl.2013.840 %X Oligo(ethylene glycol)-oligo(propylene glycol)-oligo(ethylene glycol) (OEG-OPG-OEG) triblock copolymers are hydrogel forming and extensively investigated in the field of drug release due to their biocompatibility and thermo-sensitivity. Here the synthesis and characterization of OEG-OPG-OEG based polymer networks from methacrylated oligomers by photo-irradiation are reported. Two precursors were selected to have comparable hydrophilicity (80 wt% OEG content) but different molecular weights of M n = 8400 g·mol-1 and 14600 g·mol-1. The precursor solutions were prepared in concentration 10 to 30 wt%. The resulting polymer networks prepared from high M n precursors exhibited higher swellability at equilibrium (up to 3400%) and mechanical properties in the range of G’ ∼ 0.1 to 1 kPa at 5 °C compared to networks based on low M n precursors. A more significant thermo-sensitive behavior in terms of swellability, volumetric contraction and mechanical transition, starting at 30 °C could also be observed for the networks based on high M n precursors, thus promoting future application in the field of drug release. %0 conference lecture %@ %A Behl, M.,Lendlein, A. %D 2013 %J Nanomaterials for Biomedical Applications, 3rd Sino-German Symposium 2013 %N %P %T Introduction Note %U %X %0 conference poster %@ %A Yan, W.,Fang, L.,Noechel, U.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Influence of Strain Rate on the Shape-Memory Performance of Multiblock Copolymers Comprising Crystallizable Poly(Epsilon-caprolactone) Switching and Poly[3-(S)-isobutylmorpholine-2,5-dione] Hard Segments %U %X %0 conference poster %@ %A Saatchi, M.,Behl, M.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Preparation and Characterization of Double Layer Porous Structure by Injection Molding %U %X %0 conference poster %@ %A Razzaq, M.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Geometrically Controlled Triple-Shape Effect of Polymer Nanocomposites %U %X %0 conference poster %@ %A Kusmierczuk, M.,Baudis, S.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Investigating the Influence of Water Uptake on the Mechanical Properties of Covalently Crosslinked Poly[(L-lactide)-co-glycolide] Polymer Networks %U %X %0 conference poster %@ %A Zhang, P.,Behl, M.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Influence of Metal Ions on the Mechanical Properties of Phosphine-based Coordination Polymer Networks %U %X %0 conference poster %@ %A Baudis, S.,Behl, M.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T High-Throughput Synthesis as a Technology Platform for Copolymer Libraries %U %X %0 conference poster %@ %A Fang, L.,Yan, W.,Zierke, M.,Richau, K.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Crystallization Behavior and Phase Separation in Spin Coated Copolyetherester Urethane Films with Different Diisocyanate Linkers %U %X %0 conference poster %@ %A Fang, L.,Yan, W.,Richau, K.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Crystallization Behaviors of Biodegradable Multiblock Copolymers Based on Oligodepsipeptides in Spin-coated Films %U %X %0 conference poster %@ %A Reddy, C.,Noechel, U.,Wang, K.,Cui, J.,Behl, M.,Kratz, K.,Lendlein, A. %D 2013 %J 12th International Conference on Polymers for Advanced Technologies, PAT 2013 %N %P %T Influence of co-monomer composition and covalent netpoint density on temperature-memory performance of crystallizable copolymer networks %U %X %0 journal article %@ 1946-4274 %A Schroeter, M.,Behl, M.,Weder, C.,Lendlein, A. %D 2012 %J MRS Online Proceedings Library %N %P 183-188 %R doi:10.1557/opl.2012.424 %T Synthesis and Characterization of Poly(p-phenylene ethynylene)s with nitroxyl radical endgroups %U https://doi.org/10.1557/opl.2012.424 %X The generation of terminal N-Hydroxyl substituents in p-phenylene ethynylene based compounds is presented. P-phenylene ethynylene derivatives were synthesized in a Sonogashira coupling reaction. N-Hydroxyl groups could be introduced by lithiation of iodine moieties and subsequent reaction with the 2-methyl-2-nitrosopropane generated by the cleavage of its dimer. The synthesis by lithiation was found to be more effective compared to the reaction with the Grignard reagent and the chloro-derivative. The resulting compounds were characterized by 1H NMR, UV and PL spectroscopy and were shown to be sensitive towards oxidation. This new approach of introducing additional charge carriers by nitroxyl endgroups might enable conjugated polymers with enhanced conductivity. %0 journal article %@ 1946-4274 %A Yang, D.,Feng, Y.,Behl, M.,Lendlein, A.,Zhao, H.,Khan, M.,Guo, J. %D 2012 %J MRS Online Proceedings Library %N %P 220-225 %R doi:10.1557/opl.2012.702 %T Biomimetic Hemo-compatible Surfaces of Polyurethane by Grafting Copolymer Brushes of Poly(ethylene glycol) and Poly(phosphorylcholine methacrylate) %U https://doi.org/10.1557/opl.2012.702 %X Polyurethanes (PU) have been widely used as biomaterial in recent years, while thrombus may still occur when contacting with blood especially for extended period of time. Poly(ethylene glycol) (PEG) and phosphorylcholine (PC)-based polymers are commonly employed for surface modification to create protein repellent surfaces. PC-based polymers have been investigated as biomimetic materials because PC is the major component in the outer layer of cell membranes. In this study, the biomimetic copolymer brush of PEG-b-poly(2-methacryloyloxyethyl phosphorylcholine) on PU surfaces was synthesized via atom transfer radical polymerization (ATRP) with a surface initiator. The flexible PEG chain was 200 g·mol−1, while the poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) chain length was controlled by the ratio of monomer to sacrificial initiator in solution. The topology of the modified surfaces was characterized by the phase image of atomic force microscopy (AFM) to study the synergy effect between PEG chains and poly(MPC) chains. The unmodified and modified surfaces were characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), water contact angle and platelet adhesion. The results demonstrated that efficient grafting of PEG-b-poly(MPC) brushes on the surfaces was achieved. The PU surfaces modified with PEG and phosphorylcholine zwitterionic brushes showed effective resistance to platelet adhesion and high hemocompatibility in vitro. These PEG and PC-grafted PU materials might be potentially applied in blood-contacting materials or devices due to their good mechanical and hemocompatible properties. %0 journal article %@ 1946-4274 %A Iqbal, D.,Melchert, C.,Behl, M.,Lendlein, A.,Beuermann, S. %D 2012 %J MRS Online Proceedings Library %N %P 1-6 %R doi:10.1557/opl.2012.423 %T Modeling of Free Radical Polymerization of Azobenzene-based Linear Polymers %U https://doi.org/10.1557/opl.2012.423 %X Modeling of free radical polymerizations of the liquid-crystalline monomer 6-[4-(4-heptyloxyphenylazo)phenoxy]hexylacrylate using the PREDICI software package is reported. The model accounts for all elemental reactions that were identified to be important for radical polymerizations of acrylate-type monomers. On the basis of butyl acrylate kinetic data a remarkable agreement between number average molar masses from modelling (Mn,sim) and from experiments (Mn,exp) is observed: Mn,sim = 17800 g·mol−1 and Mn,exp = 17400 g·mol−1. Similarly, dispersity values of 1.8 and 1.6 were determined via modelling and experiments, respectively. It is shown that the assumption of butyl acrylate kinetics provides a reasonable approximation even for acrylate-based monomers having mesogenic substituents. %0 journal article %@ 1438-7492 %A Balk, M.,Behl, M.,Nöchel, U.,Lendlein, A. %D 2012 %J Macromolecular Materials and Engineering %N 12 %P 1184-1192 %R doi:10.1002/mame.201200232 %T Shape-Memory Hydrogels with Switching Segments Based on Oligo(ω-pentadecalactone) %U https://doi.org/10.1002/mame.201200232 12 %X We investigated whether dual-shape hydrogels based on crosslinked N-vinyl-2-pyrrolidone can be created, in which oligo(ω-pentadecalactone) (equation image = 2900 g · mol−1, Tm = 89 °C) chain segments contribute to the switching domains. In the obtained hydrogels, the volumetric degree of swelling decreased from 480 to 190% while the E-moduli increased from 0.10 to 0.34 MPa with increasing OPDL content. Furthermore, the equilibrium swollen hydrogels displayed good shape-memory properties with strain fixity ratios above 95% and strain recovery rates above 92%. These shape-memory hydrogels, whose degree of swelling was almost independent of the temperature, might be interesting candidates for various applications such as stimuli-sensitive switches or valves. %0 journal article %@ 1946-4274 %A Yang, K.K.,Zotzmann, J.,Lendlein, A.,Behl, M. %D 2012 %J MRS Online Proceedings Library %N %P 190-195 %R doi:10.1557/opl.2012.453 %T Synthesis and Characterization of Hydroxy-telechelic Four-arm Star-shaped Oligo(tetrahydrofuran), Their Crosslinking, and Thermomechanical Investigation of the Poymer Network %U https://doi.org/10.1557/opl.2012.453 %X Here the synthesis of hydroxy-telechelic four-arm star-shaped oligotetrahydrofuran (4PTHF) with controllable molecular weight was explored, which was perfomed as living cationic ring-opening polymerization of THF using pentaerythritol and trifluoromethanesulfonicanhydride as initiation system. The molecular weights of the 4PTHF were a function of the reaction time. A polymer network was prepared from the hydroxy-telechelic 4PTHF precursor by crosslinking with diisocyanate and the shape-memory properties were determined. High values for Rf and Rr > 98% were obtained even at high programmed elongations, which suggest the 4PTHF-network as a promising shape-memory material. These materials might have a great potential, as the upscaling of synthesis could be successfully demonstrated. %0 conference lecture %@ %A Behl, M.,Lendlein, A.,Wischke, C. %D 2012 %J 9th World Biomaterials Congress %N %P %T Triple-functional polymer-based biomaterials combining controlled drug release, degradability and shape-memory capability %U %X %0 conference lecture %@ %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2012 %J 4th International Conference on Smart Materials, Structures and Systems, CIMTEC 2012 %N %P %T Memory Effects in Magnetic Nanocomposites %U %X %0 journal article %@ 1616-301X %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2012 %J Advanced Functional Materials %N 1 %P 184-191 %R doi:10.1002/adfm.201101590 %T Magnetic Memory Effect of Nanocomposites %U https://doi.org/10.1002/adfm.201101590 1 %X The magnetic memory effect (MME) is the ability of magneto-sensitive materials to remember the magnetic field strength (Hdef), at which they were deformed recently. They respond close to Hdef either by recovering their initial shape at a switching magnetic field strength Hsw under stress-free conditions or by building up stress with a peak maximum at Hσ,max under constant strain conditions. This paper explores whether such a MME can be created for polymer-based nanocomposites. The concept is based on temperature-memory polymers (TMP) as matrix, in which silica coated iron(III)oxide nanoparticles (mNP) are dispersed. The MME was explored in a cyclic magneto-mechanical test, in which the nanocomposite sample was elongated to ϵm while being exposed to an alternating magnetic field at Hdef. The magnetic memory was read out by determining Hσ,max or Hsw. A linear correlation between Hσ,max (or Hsw) and Hdef in a range from 15 to 23 kA m−1 at a fixed frequency of f = 258 kHz is observed and demonstrates the excellent magnetic memory properties of the investigated nanocomposites containing either crystallizable or amorphous, vitrifiable domains as controlling units. The deformation ϵm at Hdef can be fixed with an accuracy of more than 72% and the initial shape can be recovered almost completely by more than 86%. The MME allows the design of magnetically programmable devices such as switches or mechanical manipulators. %0 conference poster %@ %A Friess, F.,Wischke, C.,Behl, M.,Lendlein, A. %D 2012 %J Advanced Functional Polymers for Medicine, AFPM 2012 %N %P %T Oligo(Epsilon-caprolactone)-based polymer networks prepared by photocrosslinking in solution %U %X %0 conference poster %@ %A Noechel, U.,Kratz, K.,Behl, M.,Zizak, I.,Lendlein, A. %D 2012 %J Advanced Macromolecular Systems Across the Length Scales, AMSALS 2012 %N %P %T Nanostructural Changes of Temperature-Memory Polymers With Crystallizable Controlling Units Explored by SAXS/WAXS %U %X %0 conference poster %@ %A Behl, M.,Razzaq, M.,Lendlein, A. %D 2012 %J Fachgruppentagung der GDCH Fachgruppe Makromolekulare Chemie - Smart Polymers %N %P %T Thermo-mechanical Characterization of Nanocomposites based on Oligo(Omega-pentadecalactone) and Magnetite Nanoparticles %U %X %0 conference poster %@ %A Behl, M.,Zotzmann, J.,Lendlein, A. %D 2012 %J 9th World Biomaterial Congress %N %P %T Copolymer Networks with Triple-shape Capability %U %X %0 conference poster %@ %A Tzoneva, R.,Seifert, B.,Behl, M.,Lendlein, A. %D 2012 %J 31. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %N %P %T Elastic multiblock copolymers for vascular regeneration: Protein adsorption and hemocompatibility %U %X %0 journal article %@ 1788-618X %A Kumar, U.N.,Kratz, K.,Behl, M.,Lendlein, A. %D 2012 %J eXPRESS Polymer Letters %N 1 %P 26-40 %R doi:10.3144/expresspolymlett.2012.4 %T Shape-memory properties of magnetically active triple-shape nanocomposites based on a grafted polymer network with two crystallizable switching segments %U https://doi.org/10.3144/expresspolymlett.2012.4 1 %X Thermo-sensitive shape-memory polymers (SMP), which are capable of memorizing two or more different,shapes, have generated significant research and technological interest. A triple-shape effect (TSE) of SMP can be activated e.g. by increasing the environmental temperature (Tenv), whereby two switching temperatures (Tsw) have to be exceeded to enable the subsequent shape changes from shape (A) to shape (B) and finally the original shape (C).,In this work, we explored the thermally and magnetically initiated shape-memory properties of triple-shape nanocomposites with various compositions and particle contents using different shape-memory creation procedures (SMCP). The,nanocomposites were prepared by the incorporation of magnetite nanoparticles into a multiphase polymer network matrix with grafted polymer network architecture containing crystallizable poly(ethylene glycol) (PEG) side chains and poly(Epsilon-caprolactone) (PCL) crosslinks named CLEGC.,Excellent triple-shape properties were achieved for nanocomposites with high PEG weight fraction when two-step programming procedures were applied. In contrast, single-step programming resulted in dual-shape properties for all investigated,materials as here the temporary shape (A) was predominantly fixed by PCL crystallites. %0 journal article %@ 1386-0291 %A Tzoneva, R.,Seifert, B.,Behl, M.,Lendlein, A. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 337-348 %R doi:10.3233/CH-2012-1609 %T Elastic multiblock copolymers for vascular regeneration: Protein adsorption and hemocompatibility %U https://doi.org/10.3233/CH-2012-1609 2-4 %X Hemocompatibility of elastic multiblock copolymers PDC, based on poly(p-dioxanone) (PPDO)/poly(ε-caprolactone)-segments, capable of a shape-memory effect, and PDD, based on PPDO/poly((adipinate-alt-1,4-butanediol)-co-(adipinate-alt-ethylene glycol)-co-adipinate-alt-diethylene glycol)-segments, was studied in order to assess their suitability for an application aiming at blood vessels regeneration. The results were compared with polypropylene (PP) which is a widely used blood-contacting material for devices as blood oxygenators and dialysis tubes. Protein adsorption studies showed diverse blood plasma proteins in a relatively high amount on both elastic polymers compared to the poor amount of plasma proteins adsorbed on PP. Study of the coagulation system revealed high thrombin formation on PDC and no difference in plasma kallikrein activation between elastic multiblock copolymers and the reference PP. Activation of complement system was higher for PDC followed by PDD and lower for PP. However, platelet adhesion and activation were hardly suppressed on the multiblock copolymers compared to the PP surface, where the number of adhered platelets and the activation rate were significant. The present results reveal that the tested multiblock copolymers with improved elastic properties and shape-memory capability (PDC) show low thrombogenicity and are promising candidates for vascular tissue engineering. %0 journal article %@ 0959-9428 %A Razzaq, M.Y.,Behl, M.,Frank, U.,Koetz, J.,Szczerba, W.,Lendlein, A. %D 2012 %J Journal of Materials Chemistry %N %P 9237-9243 %R doi:10.1039/c2jm16146j %T Oligo(Omega-pentadecalactone) decorated magnetic nanoparticles %U https://doi.org/10.1039/c2jm16146j %X Hybrid magnetic nanoparticles (mgNP) with a magnetite core diameter of 10 ± 1 nm surface functionalized with oligo(ω-pentadecalactone) (OPDL) oligomers with Mn between 1300 and 3300 g mol−1 could be successfully prepared having OPDL grafted from 200 mg g−1 to 2170 mg g−1. The particles are dispersible in chloroform resulting in stable suspensions. Magnetic response against an external magnetic field proved the superparamagnetic nature of the particles with a low coercivity (Bc) value of 297 µT. The combination of the advantageous superparamagnetism of the mgNP with the exceptional stability of OPDL makes these novel hybrid mgNP promising candidates as multifunctional building blocks for magnetic nanocomposites with tunable physical properties. %0 conference poster %@ %A Scharnagl, N.,Hiebl, B.,Trescher, K.,Zierke, M.,Behl, M.,Kratz, K.,Jung, F.,Lendlein, A. %D 2012 %J 31. Jahrestagung der Deutschen Gesellschaft fuer klinische Mikrozirkulation und Haemorheologie %N %P %T Behaviour of fibroblasts on water born acrylonitrile based copolymers with different densities of positive and negative surface charges %U %X %0 journal article %@ 1386-0291 %A Scharnagl, N.,Hiebl, B.,Trescher, K.,Zierke, M.,Behl, M.,Kratz, K.,Jung, F.,Lendlein, A. %D 2012 %J Clinical Hemorheology and Microcirculation %N 2-4 %P 295-311 %R doi:10.3233/CH-2012-1606 %T Behaviour of fibroblasts on water born acrylonitrile-based copolymers containing different cationic and anionic moieties %U https://doi.org/10.3233/CH-2012-1606 2-4 %X The chemical composition of a substrate can influence the adhesion, viability and proliferation of cells seeded on the substrate. The aim of this work was to investigate the influence of different cationic or anionic moieties in acrylonitrile-based copolymers on the interaction with fibroblasts. A series of ten different types of acrylonitrile-based copolymers with a random sequence structure was prepared using a water born synthesis process to exclude potential residues of organic solvents. As charged comonomers cationic methacrylic acid-2-aminoethylester hydrochloride (AEMA), N-3-amino-propyl-methacrylamide hydrochloride (APMA) and anionic 2-methyl-2-propene-1-sulfonic acid sodium salt (NaMAS) were utilized. By application of a specific sintering procedure the copolymer materials were processed into transparent disks for conducting cell tests in direct contact. The copolymers were analyzed with respect to their composition and surface properties. Cytotoxicity tests of the polymer extracts, as well as of the disks were performed with L929 mouse fibroblasts. All copolymers showed no cytotoxic effects. Furthermore, for higher molar ratios of AEMA an increase in cell growth could be observed, which might be a hint that higher charge densities are favorable for the proliferation of L929 cells. %0 journal article %@ 1946-4274 %A Melchert, C.,Behl, M.,Lendlein, A. %D 2012 %J MRS Online Proceedings Library %N %P 79-84 %R doi:10.1557/opl.2012.369 %T Phase Transition Behavior of Main Chain Nematic Liquid-Crystalline Polymers Based on 2-methyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone and 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone %U https://doi.org/10.1557/opl.2012.369 %X The control of phase transition behavior in liquid crystalline polymers could enable potential application in the field of actuators and sensors by enabling a higher actuator performance of liquid crystalline elastomers (LCE). In this context the phase transition behavior of siloxane based liquid crystalline copolymers synthesized from 1,1,3,3-tetramethyldisiloxane, 2-methyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone (M-MeHq), and 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone (M-tBHq) was explored. The selected monomers provided different thermal stabilities of the nematic phase, while the non-flexible siloxane spacer suppressed a smectic phase. The mesogenic properties were studied by means of differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and wide angle X-ray scattering (WAXS). With increasing fraction of M-MeHq the nematic phase of the copolymer was stabilized and a tailoring of relatively low TNI was achieved. %0 journal article %@ 1438-7492 %A Melchert, C.,Behl, M.,Noechel, U.,Lendlein, A. %D 2012 %J Macromolecular Materials and Engineering %N 12 %P 1203-1212 %R doi:10.1002/mame.201200238 %T Influence of Comesogens on the Thermal and Actuation Properties of 2-tert-Butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone Based Nematic Main-Chain Liquid Crystalline Elastomers %U https://doi.org/10.1002/mame.201200238 12 %X Although the shape-changing capabilities of LCEs hold great potential for applications ranging from micropumps to artificial muscles, customization of the LCE functionality to the applications' requirements is still a challenge. It is studied whether the orientation of NMC-LCPs and NMC-LCEs based on 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone can be enhanced by copolymerization with 2-methyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone or 2,6-bis[4-(4-pentenyl-oxy)-benzoyl]anthracene. An increasing content of the comonomers stabilizes the nematic phase, which enables a tailoring of TNI for the NMC-LCP between 45 and 68 °C, while for the NMC-LCE TNI ranges between 69 and 76 °C. In addition, NMC-LCE show an increased actuation performance. %0 conference lecture (invited) %@ %A Neffe, A.T.,Behl, M.,Jung, F.,Pierce, B.F.,Lendlein, A. %D 2012 %J Smart Collaborations Seminar %N %P %T Biopolymer-Based Materials for Medical Applications %U %X %0 conference lecture %@ %A Behl, M.,Ridder, U.,Kelch, S.,Lendlein, A. %D 2012 %J 9th World Biomaterials Congress %N %P %T Blending of Degradable Multiblock Copolymers creates Shape- Memory Materials %U %X %0 journal article %@ %A Neffe, A.T.,Scharnagl, N.,Behl, M.,Lendlein, A. %D 2012 %J BioTOPics : Journal of Biotechnology in Berlin-Brandenburg %N %P 8-10 %T Biomaterials in Regenerative Medicine %U %X Regenerative Therapies require biomaterials with properties and functions tailored to the tion' demands of a specific applica- Especially in biomaterial induced auto-regeneration, multifunctional polymer-based biomaterials are of high rel- evance' The cooperation of scientists from different disciplines is essential in order to perform research and development,of biomaterials directed to clinical applications and products. Here, fundamental research for polymer based biomaterials,meets application-motivated science aiming at translation of the gained knowledge into products and clinical applications. %0 conference lecture (invited) %@ %A Behl, M.,Feng, Y.,Zotzmann, J.,Razzaq, M.,Lendlein, A. %D 2012 %J Kolloqium des Brandernburger Polymerverbandes %N %P %T Recent Developments in Shape-Memory and Triple-Shape Materials %U %X %0 journal article %@ 1946-4274 %A Zotzmann, J.,Behl, M.,Lendlein, A. %D 2012 %J MRS Online Proceedings Library %N %P 43-48 %R doi:10.1557/opl.2012.250 %T Triple-Shape Effect of Copolymer Networks Based on Poly(Omega-pentadecalactone) and Poly(Epsilon-caprolactone) Segments Applying a Programming Procedure with an Adjusted Temperature Profile %U https://doi.org/10.1557/opl.2012.250 %X A triple-shape material based on the two crystallizable segments poly(ω‑pentadeca-lactone) and poly(ε-caprolactone) was synthesized by crosslinking star-shaped precursors. A newly developed programming procedure (TSCP2) was applied in order to achieve triple-shape behavior. The application of this modified triple-shape creation procedure enabled triple-shape capability by influencing the crystallization behavior of the two switching segments in these copolymer networks, which partly show no two distinct and separated melting points. The influence of molecular weight and content of the poly(ε-caprolactone) segment on the triple-shape effect programmed by application of TSCP2 was investigated. %0 journal article %@ 2280-8000 %A Melchert, C.,Yongvongsoontorn, N.,Behl, M.,Lendlein, A. %D 2012 %J Journal of Applied Biomaterials & Functional Materials %N 3 %P 185-190 %R doi:10.5301/JABFM.2012.10364 %T Synthesis and characterization of telechelic oligoethers with terminal cinnamylidene acetic acid moieties %U https://doi.org/10.5301/JABFM.2012.10364 3 %X Purpose: The formation of photoresponsive hydrogels were reported by irradiation of star-shaped poly(ethylene glycol)s with terminal cinnamylidene acetic acid (CAA) groups, which are capable of a photoinduced [2+2] cycloaddition. In this study we explored whether oligo(ethylene glycol)s and oligo(propylene glycol)s of varying molecular architecture (linear or star-shaped) or molecular weights could be functionalized with CAA as terminal groups by esterification or by amide formation.
Methods: Oligo(ethylene glycol) (OEG) and oligo(propylene glycol) (OPG) with varying molecular architecture (linear, star-shaped) and weight average molecular weights between 1000 and 5000 g.mol-1 were functionalized by means of esterification of hydroxyl or amine endgroups with cinnamylidene acetic acid (CAA) or cinnamylidene acetyl chloride (CAC) as telechelic endgroups. The chemical structure, thermal properties, and molecular weights of the oligoethers obtained were determined by NMR spectroscopy, UV spectroscopy, DSC, and MALDI-TOF.
Results: CAA-functionalized linear and star-shaped OEGs or OPGs could be obtained with a degree of functionalization higher than 90%. In MALDI-TOF measurements an increase in Mw of about 150 g∙mol-1 (for each terminal end) after the functionalization reaction was observed. OEGCAA and OPGCAA showed an increase in glass transition temperature (Tg) from about -70°C to -50°C, compared to the unfunctionalized oligoethers. In addition, the melting temperature (Tm ) of OEGCAA decreased from about 55°C to 30°C, which can be accounted for by the hampered crystallization of the precursors because of the bulky CAA end groups as well as by the loss of the hydroxyl telechelic end groups.
Conclusion: The synthesis of photoresponsive oligoethers containing cinnamylidene acetic acid as telechelic endgroup was reported and high degrees of functionalization could be achieved. Such photosensitive oligomers are promising candidates as reactive precursors, for the preparation of biocompatible high molecular weight polymers and polymer networks. %0 journal article %@ 2280-8000 %A Tartivel, L.,Behl, M.,Schroeter, M.,Lendlein, A. %D 2012 %J Journal of Applied Biomaterials & Functional Materials %N 3 %P 243-248 %R doi:10.5301/JABFM.2012.10295 %T Hydrogel networks based on ABA triblock copolymers %U https://doi.org/10.5301/JABFM.2012.10295 3 %X Background: Triblock copolymers from hydrophilic oligo(ethylene glycol) segment A and oligo(propylene glycol) segment B, providing an ABA structure (OEG-OPG-OEG triblock), are known to be biocompatible and are used as self-solidifying gels in drug depots. A complete removal of these depots would be helpful in cases of undesired side effects of a drug, but this remains a challenge as they liquefy below their transition temperature. Therefore we describe the synthesis of covalently cross-linked hydrogel networks. Method: Triblock copolymer-based hydrogels were created by irradiating aqueous solutions of the corresponding macro-dimethacrylates with UV light. The degree of swelling, swelling kinetics, mechanical properties and morphology of the networks were investigated. Results: Depending on precursor concentration, equilibrium degree of swelling of the films ranged between 500% and 880% and was reached in 1 hour. In addition, values for storage and loss moduli of the hydrogel networks were in the 100 Pa to 10 kPa range. Conclusion: Although OEG-OPG-OEG triblocks are known for their micellization, which could hamper polymer network formation, reactive OEG-OPG-OEG triblock oligomers could be successfully polymerized into hydrogel networks. The degree of swelling of these hydrogels depends on their molecular weight and on the oligomer concentration used for hydrogel preparation. In combination with the temperature sensitivity of the ABA triblock copolymers, it is assumed that such hydrogels might be beneficial for future medical applications – e.g., removable drug release systems. %0 conference poster %@ %A Tartivel, L.,Behl, M.,Schroeter, M.,Lendlein, A. %D 2012 %J Advanced Functional Polymers for Medicine, AFPM 2012 %N %P %T Hydrogel Networks Based on ABA Triblock Copolymers %U %X %0 conference lecture %@ %A Melchert, C.,Yongvongsoontorn, N.,Behl, M.,Lendlein, A. %D 2012 %J Polydays 2012 %N %P %T Synthesis and Characterization of Telechelic Oligoethers with Terminal Cinnamyliden Acetic Acid Moieties %U %X %0 conference paper %@ %A Zotzmann, J.,Behl, M.,Lendlein, A. %D 2012 %J MRS Symposium Proceedings, Multifunctional Polymer-Based Materials, 2011 MRS Fall Meeting %N %P 85-90 %T Triple-Shape Effect of Copolymer Networks Based on Poly(Omega-pentadecalactone) and Poly(Epsilon-caprolactone) Segments Applying a Programming Procedure with an Adjusted Temperature Profile %U %X %0 conference paper %@ %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2012 %J MRS Symposium Proceedings, Multifunctional Polymer-Based Materials, 2011 MRS Fall Meeting %N %P 3-8 %T Shape-Memory Properties of Nanocomposites based on Poly(Omega-pentadecalactone) and Magnetic Nanoparticles %U %X %0 journal article %@ 1946-4274 %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2012 %J MRS Online Proceedings Library %N %P 19-24 %R doi:10.1557/opl.2012.222 %T Shape-Memory Properties of Nanocomposites based on Poly(Omega-pentadecalactone) and Magnetic Nanoparticles %U https://doi.org/10.1557/opl.2012.222 %X Magneto-sensitive shape-memory polymers (SMP) obtained by incorporating magnetic nanoparticles in a SMP matrix are an emerging class of multifunctional materials. The incorporation of the nanoparticles enhanced the mechanical properties and in addition enabled remote actuation by exposure to alternating magnetic fields. Here, we report on the thermallyinduced shape-memory properties of such magneto-sensitive nanocomposites based on poly(ω- pentadecalactone) (PPDL) switching segments and magnetic nanoparticles. A series of nanocomposites were prepared by crosslinking of poly(ω-pentadecalactone)dimethacrylate (Mn = 2800 g·mol-1and 5100 g·mol-1) in the presence of silica encapsulated magnetic nanoparticles. The silica shell of the nanoparticles was selected to enhance the distribution and compatibility of the nanoparticles with the polymer matrix. Thermal and mechanical properties of the nanocomposites were explored as a function of PPDL chain length and nanoparticle weight content. All nanocomposites exhibited excellent shape-memory properties with shape fixity rates between 86% and 93% and shape recovery rates above 97%. Potential applications for such shape-memory nanocomposites include smart implants, medical instruments, which could be controlled on demand by thermal or indirect magnetic heating. %0 conference poster %@ %A Kumar, U.N.,Kratz, K.,Behl, M.,Lendlein, A. %D 2012 %J German-Russian Conference on Fundamentals and Applications of Nanoscience %N %P %T Triple-shape Nanocomposites with Adaptable Apparent Switching Temperatures %U %X %0 conference lecture %@ %A Behl, M.,Feng, Y.,Lendlein, A. %D 2012 %J 4th International Conference on Smart Materials, Structures and Systems, CIMTEC 2012 %N %P %T Biocompatible, Degradable Multiblock Copolymers with Polydepsipeptide-segments and Shape-memory Properties %U %X %0 conference lecture %@ %A Melchert, C.,Behl, M.,Lendlein, A. %D 2012 %J 4th International Conference on Smart Materials, Structures and Systems, CIMTEC 2012 %N %P %T Plasma treatment of LCE affects thermal properties of shape-changing materials %U %X %0 conference poster %@ %A Melchert, C.,Yongvonsoontorn, N.,Behl, M.,Lendlein, A. %D 2012 %J Advanced Functional Polymers for Medicine, AFPM 2012 %N %P %T Synthesis and Characterization of Telechelic Oligoethers with Terminal Cinnamyliden Acetic Acid Moieties %U %X %0 conference lecture %@ %A Behl, M.,Feng, Y.,Lendlein, A. %D 2012 %J 9th World Biomaterials Congress %N %P %T Degradable Multiblock Shape-Memory Copolymers Having Polydepsipeptide- and Poly(ε-caprolactone)segments as Biomaterials %U %X %0 conference lecture %@ %A Behl, M.,Zotzmann, J.,Lendlein, A. %D 2012 %J 24th International Liquid Crystal Conference, ILCC 2012 %N %P %T Dual and Triple-Shape Properties of Poly(Omega-pentadecalactone)-based Polymer Networks %U %X %0 conference lecture %@ %A Lendlein, A.,Behl, M.,Kratz, K. %D 2012 %J 24th International Liquid Crystal Conference, ILCC 2012 %N %P %T Multifunctional Shape-Memory Polymers %U %X %0 journal article %@ 1381-5148 %A Kaiser, C.,Behl, M.,Schroeter, M.,Kratz, K.,Lendlein, A. %D 2012 %J Reactive and Functional Polymers %N 8 %P 533-541 %R doi:10.1016/j.reactfunctpolym.2012.04.015 %T Dicarboxy-telechelic cooligomers with sequence structure tunable light absorption %U https://doi.org/10.1016/j.reactfunctpolym.2012.04.015 8 %X Alternating cooligomers of 5 pyrrole (P) and thiophene (T) units with a PTPTP sequence and carboxylic telechelic groups in α,α′-position are supposed to provide a low band gap and might be incorporated into degradable polymers. In this study we explored whether such new α,α′-ester linked π-conjugated alternating electron rich PTPTP cooligomers of defined size could be created following a Stille coupling synthesis pathway. The obtained cooligomers displayed in the absorption spectra λmax between 341 and 379 nm in solution and between 346 and 410 nm in the solid state, which could be tuned by the substitution with donor type alkyl and alkoxy functions. A strong red shift of the absorption bands into the IR region of the spectrum with absorption maxima between 550 and 650 nm and further to 850 and 1000 nm could be obtained when additional charges by deprotonation or oxidation were introduced. The prepared semi conducting materials could be applied potentially as dyes for photoacoustic imaging or in sensors for oxidation monitoring. %0 conference lecture %@ %A Balk, M.,Behl, M.,Noechel, U.,Lendlein, A. %D 2012 %J 4th International Conference on Smart Materials, Structures and Systems, CIMTEC 2012 %N %P %T Shape-Memory Hydrogels with Switching Segments Based on Oligo(Omega-pentadecalactone) %U %X %0 journal article %@ 2040-3364 %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2012 %J Nanoscale %N 20 %P 6181-6195 %R doi:10.1039/c2nr31332d %T Memory-effects of magnetic nanocomposites %U https://doi.org/10.1039/c2nr31332d 20 %X The thermally induced shape memory effect (SME) is the capability of a material to fix a temporary (deformed) shape and recover a ‘memorized’ permanent shape in response to heat. SMEs in polymers have enabled a variety of applications including deployable space structures, biomedical devices, adaptive optical devices, smart dry adhesives and fasteners. By the incorporation of magnetic nanoparticles (mNP) into shape-memory polymer (SMP), a magnetically controlled SME has been realized. Magnetic actuation of nanocomposites enables remotely controlled devices based on SMP, which might be useful in medical technology, e.g. remotely controlled catheters or drug delivery systems. Here, an overview of the recent advances in the field of magnetic actuation of SMP is presented. Special emphasis is given on the magnetically controlled recovery of SMP with one switching temperature Tsw (dual-shape effect) or with two Tsws (triple-shape effect). The use of magnetic field to change the apparent switching temperature (Tsw,app) of the dual or triple-shape nanocomposites is described. Finally, the capability of magnetic nanocomposites to remember the magnetic field strength (H) initially used to deform the sample (magnetic-memory effect) is addressed. The distinguished advantages of magnetic heating over conventional heating methods make these multifunctional nanocomposites attractive candidates for in vivo applications. %0 conference paper %@ %A Melchert, C.,Behl, M.,Lendlein, A. %D 2012 %J MRS Symposium Proceedings, Multifunctional Polymer-Based Materials, 2011 MRS Fall Meeting %N %P 119-124 %T Phase Transition Behavior of Main Chain Nematic Liquid-Crystalline Polymers Based on 2-methyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone and 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone %U %X %0 book part %@ %A Behl, M.,Lendlein, A. %D 2011 %J Kirk-Othmer Encyclopedia of Chemical Technology %N %P 1-16 %R doi:10.1002/0471238961.1908011612051404.a01.pub2 %T Shape-Memory Polymers %U https://doi.org/10.1002/0471238961.1908011612051404.a01.pub2 %X Shape-memory polymers (SMP) are an emerging class of active materials, which are able to change their shape in a predefined way upon appropriate stimulation. SMP, which can switch from a temporary to their permanent shape, are dual-shape materials. Here fundamental aspects concerning the design of suitable polymer architectures as well as of tailored programming processes are presented. Furthermore, the influence of various physical parameters on the shape recovery is discussed. Shape-memory research initially was focused on the thermally induced dual shape-effect. Presently, this research field is rapidly developing in two major areas. On the one hand other stimuli are being realized by either indirect thermal actuation or direct actuation by addressing stimuli-sensitive groups on the molecular level. On the other hand the programmed shape changes are getting more complex. Triple-shape materials are able to perform two subsequent on-demand shape changes and multishape materials are extending this to even more steps. %0 journal article %@ 0935-9648 %A Kumar, U.N.,Kratz, K.,Heuchel, M.,Behl, M.,Lendlein, A. %D 2011 %J Advanced Materials %N 36 %P 4157-4162 %R doi:10.1002/adma.201102251 %T Shape-Memory Nanocomposites with Magnetically Adjustable Apparent Switching Temperatures %U https://doi.org/10.1002/adma.201102251 36 %X The apparent switching temperatures (Tsw,app), which need to be exceeded by the environmental temperature (Tenv) to initialize a shape-memory effect (SME) in magnetosensitive dual- or triple-shape composites, are systematically adjusted by application of a constant weak alternating magnetic field. This adaptation of Tsw,app is fully reversible and results from the combination of environmental and inductive heating. %0 book part %@ %A Lendlein, A.,Wischke, C.,Kratz, K.,Heuchel, M.,Zotzmann, J.,Hiebl, B.,Neffe, A.,Behl, M. %D 2011 %J Comprehensive Biomaterials %N %P 479-496 %T Shape- Memory Polymers %U %X Medical devices such as implants, surgical instruments, extracorporal devices or wound covers, as well as controlled drug delivery systems (CDDS) require a specific combination of material properties and functions including, e.g., mechanical stability, biocompatibility, or biofunctionality. Polymeric biomaterials are of high relevance for such applications, as properties and functions can be tuned in a wide range by only small defined variations of their chemical or morphological structure. The rapid progress in surgical techniques, especially in minimally-invasive surgery, requires smart materials, which are capable of an active on-demand movement and which do not need to be removed in a second surgery. These challenges can be addressed by shape-memory polymers (SMPs) described in this chapter. SMPs are of high technological significance for biomedical applications as they enable on demand predefined changes in the shape of a device upon exposure to a suitable stimulus. Multifunctional materials are obtained when the shape-memory effect is combined with an additional function such as hydrolytic degradability, biofunctionality, and controlled drug release. Selected biomaterials with shape-memory capability are presented, including data on their biocompatibility. The potential of SMPs as a platform technology for biomedical applications is sketched by an overview on SMP-based medical devices being developed and the potential use of SMPs as matrix for CDDS. %0 journal article %@ 0920-5063 %A Tzoneva, R.,Weckwerth, C.,Seifert, B.,Behl, M.,Heuchel, M.,Tsoneva, I.,Lendlein, A. %D 2011 %J Journal of Biomaterials Science - Polymer Edition %N 16 %P 2205-2226 %R doi:10.1163/092050610X537147 %T In Vitro Evaluation of Elastic Multiblock Co-polymers as a Scaffold Material for Reconstruction of Blood Vessels %U https://doi.org/10.1163/092050610X537147 16 %X There is a need to create cell- and histocompatible implant materials, which might temporarily replace the mechanical function of a native tissue for regenerative therapies. To match the elastic behavior of the native tissue two different multiblock co-polymers were investigated: PDC, consisting of poly(p-dioxanone) (PPDO)/poly(ɛ-caprolactone) (PCL), and PDD, based on PPDO/poly((adipinate-alt-1,4-butanediol)-co-(adipinate-alt-ethylene glycol)-co-adipinate-alt-diethylene glycol) (Diorez). PDC is capable of a shape-memory effect. Both multiblock co-polymers show an improved elasticity compared to materials applied in established vascular prosthesis. PDD is softer than PDC at 20°C, while PDC maintains its elasticity at 37°C. Thermodynamic characteristics indicate a more polar surface of PDD. Low cell adhesion was found on surfaces with low molar free energy of hysteresis (ΔG) derived from contact angle measurements in wetting and dewetting mode and high cell adhesion on high-ΔG surfaces. An increasing content of PCL in PDC improved cell adhesion and spreading of human umbilical vein endothelial cells. The prothrombotic potential of PDD is higher than PDC. Finally, it is concluded that PDC is a promising material for vascular tissue engineering because of its improved elastic properties, as well as balanced prothrombotic and anti-thrombotic properties with endothelial cells. %0 journal article %@ 0391-3988 %A Pierce, B.F.,Bellin.K.,Behl, M.,Lendlein, A. %D 2011 %J The International Journal of Artificial Organs %N 2 %P 172-179 %R doi:10.5301/IJAO.2011.6413 %T Demonstrating the influence of water on shape-memory polymer networks based on poly[(rac-lactide)-co-glycolide] segments in vitro %U https://doi.org/10.5301/IJAO.2011.6413 2 %X Thermally-responsive shape-memory polymers (SMP) are highly promising implant materials for applications in minimally-invasive surgery since the shape-memory effect (SME) enables the implantation of a bulky device in a compressed temporary state through a small incision. When heated to a temperature exceeding the material switching temperature (Tsw), the device recovers its original bulky shape. Therefore, SMP implants with Tsw ~ 37°C are required for such applications because the body cannot withstand excessive applications of heat. Here, Tsw of networks based on poly[(rac-lactide)-co-glycolide] star-shaped macrotriol or macrotetrols with 19-22 wt% glycolide content, varying oligomer molecular weight (Mn=3000-10000 g·mol-1), and netpoint functionality (f=3 or 4) were lowered from 55-66°C to below body temperature via the uptake of water, which also induced SME at body temperature. Programmed samples kept their temporary shape at room temperature in water as well as at 37°C under dry conditions but recovered in 37°C water. Water uptake/swelling studies and FTIR analysis indicated that the mechanism of solvent-induced SME involved the plasticization of water in switching domains as opposed to changes in swelling or hydrogen bonding. This indirect actuation of SME by using a combination of solvent and heat could be exploited in easy-to-handle shape-memory implant with slower degradation kinetics. %0 journal article %@ 0391-3988 %A Behl, M.,Zotzmann, J.,Lendlein, A. %D 2011 %J The International Journal of Artificial Organs %N 2 %P 231-237 %R doi:10.5301/IJAO.2011.6424 %T One-way and reversible dual-shape effect of polymer networks based on polypentadecalactone segments %U https://doi.org/10.5301/IJAO.2011.6424 2 %X A series of degradable polymer networks containing poly(ω-pentadecalactone) (PPD) switching segments showing a thermally-induced shape-memory effect were synthesized by co-condensation of,PPD-macrotriols or -tetrols with an aliphatic diisocyanate. Thermal and mechanical properties at different,temperatures were explored for polymer networks as a function of crosslink density by varying the,polymer chain segment length or the netpoint functionality. All polymer networks exhibited excellent,shape-memory properties with shape recovery rates Rr between 99% and 100% determined in the 5th,cycle under stress-free conditions. Furthermore, the polymer networks were capable of a reversible,dual-shape effect based on crystallization induced elongation (CIE) and melting-induced contraction,(MIC) in cyclic, thermomechanical experiments under constant stress. In these tests, the polymer networks,were capable of a shape-change of 130% elongation. The associated temperatures at which,CIE or MIC occurred (TCIE and TMIC ) were shown to be a function of the applied stress. By an increase,of stress of 1.6 MPa, TCIE could be increased by 10 K. %0 journal article %@ 2095-0179 %A Wang, H.,Feng, Y.,Behl, M.,Lendlein, A.,Zhao, H.,Xiao, R.,Lu, J.,Zhang, L.,Guo, J. %D 2011 %J Frontiers of Chemical Science and Engineering %N 3 %P 392-400 %R doi:10.1007/s11705-011-1202-0 %T Hemocompatible polyurethane/gelatin-heparin nanofibrous scaffolds formed by a bi-layer electrospinning technique as potential artificial blood vessels %U https://doi.org/10.1007/s11705-011-1202-0 3 %X In this paper, a scaffold, which mimics the morphology and mechanical properties of a native blood vessel is reported. The scaffold was prepared by sequential bi-layer electrospinning on a rotating mandrel-type collector. The tubular scaffolds (inner diameter 4 mm, length 3 cm) are composed of a polyurethane (PU) fibrous outer-layer and a gelatin-heparin fibrous inner-layer. They were fabricated by electrospinning technology, which enables control of the composition, structure, and mechanical properties of the scaffolds. The microstructure, fiber morphology and mechanical properties of the scaffolds were examined by means of scanning electron microscopy (SEM) and tensile tests. The PU/gelatinheparin tubular scaffolds have a porous structure. The scaffolds achieved a breaking strength (3.7±0.13 MPa) and an elongation at break (110±8%) that are appropriate for artificial blood vessels. When the scaffolds were immersed in water for 1 h, the breaking strength decreased slightly to 2.2±0.3 MPa, but the elongation at break increased to 145±21%. In platelet adhesion tests the gelatin-heparin fibrous scaffolds showed a significant suppression of platelet adhesion. Heparin was released from the scaffolds at a fairly uniform rate during the period of 2nd day to 9th day. The scaffolds are expected to mimic the complex matrix structure of native arteries, and to have good biocompatibility as an artificial blood vessel owing to the heparin release. %0 report part %@ %A Neffe, A.T.,Behl, M.,Lendlein, A. %D 2011 %J Technologiereport - Regenerative Medizin in Berlin-Brandenburg %N %P 73-75 %T Polymere %U %X %0 journal article %@ 0391-3988 %A Yoba N’Goma, P.,Radke, W.,Malz, F.,Ziegler, H.J.,Zierke, M.,Behl, M.,Lendlein, A. %D 2011 %J The International Journal of Artificial Organs %N 2 %P 110-119 %R doi:10.5301/IJAO.2011.6409 %T Characterization of multiblock copolymers by chromatographic techniques %U https://doi.org/10.5301/IJAO.2011.6409 2 %X Multiblock copolymers (MBC) composed of blocks of poly(1,4-dioxanone) (PPDO) and poly(e-caprolactone) (PCL) were investigated in order to gain information on the extend of chemical heterogeneity of the samples. A gradient chromatographic method was established allowing separation of purely PPDO- from purely PCL-containing chains. Application of the gradient to MBC made of PPDO- and PCL-diols connected by trimethylhexamethylene diisocyanate (TMDI) resulted in two well separated peaks which were analyzed by means of FTIR, 1H-NMR and pyrolysis GC-MS. It was shown that the first peak was composed to a large extent of PPDO and only lower amounts of PCL were incorporated. Conversely, the second peak consisted predominantly of PCL with only a minor fraction of PPDO. Thus, the MBCs having PPDO and PCL segments show an unexpected broad chemical heterogeneity. %0 conference lecture %@ %A Behl, M.,Zotzmann, J.,Feng, Y.,Lendlein, A. %D 2011 %J 3rd International Conference on Smart Materials and Nanotechnology in Engineering, SMN 2011 %N %P %T Triple-shape effect of copolymer networks based on polypentadecalactone- and poly(Epsilon-caprolactone)-segments %U %X %0 journal article %@ 1386-0291 %A Battig, A.,Hiebl, B.,Feng, Y.,Lendlein, A.,Behl, M. %D 2011 %J Clinical Hemorheology and Microcirculation %N 1-3 %P 161-172 %R doi:10.3233/CH-2011-1391 %T Biological evaluation of degradable, stimuli-sensitive multiblock copolymers having polydepsipeptide- and poly(Epsilon-caprolactone) segments in vitro %U https://doi.org/10.3233/CH-2011-1391 1-3 %X Polydepsipeptides, alternating copolymers consisting of α-amino acids and α-hydroxy acids, are degradable polymers. Depsipeptide-based polymers of varied architectures can be synthesized via ring-opening polymerization of various morpholine-2,5-dione derivatives. Thermoplastic phase-segregated multiblock copolymers with poly(ε-caprolactone) (PCL) and poly(iso-butyl-morpholinedione) segments have been synthesized from the macrodiols and an aliphatic diisocyanate as a coupling agent. The respective multiblock copolymers showed shape-memory capabilities and good elastic properties, making them attractive candidates for potential application as biomaterials for controlled drug release systems, scaffolds to be applied in tissue engineering or biofunctional implants. Thus, these abilities cumulate to form multifunctional materials, combining degradability with shape-memory capability. The advantages of depsipeptide-based multiblock copolymers compared to previously reported poly(ether)ester-derived biomaterials having shape-memory property may result from their different degradation products, as the resulting α-amino acids may act as a buffer for the hydroxy acids, thereby stabilizing pH values. In this context, we report on the biological evaluation of material samples in accordance with international standards (EN DIN ISO 10993-5 and 10993-12). Here, extracts of the substrates were exposed to a continuous fibroblast like cell line (L929) to study cytocompatibility of extractable substrates. Cell viability, morphology, LDH-release (as a parameter for the functional integrity of the cell membrane), activity of the mitochondrial dehydrogenases (as a parameter of the cell activity) and assembly of the actin- and vinculin cytoskeleton indicated no incompatibilities between the extracts and L929 cells. These results suggest that depsipeptide-based multiblock copolymers are promising candidates for soft, multifunctional implant materials. %0 conference lecture %@ %A Behl, M.,Zotzmann, J.,Feng, Y.,Lendlein, A. %D 2011 %J MRS Fall 2011 Meeting %N %P %T Triple-Shape Effect of Copolymer Networks %U %X %0 journal article %@ 1432-9778 %A Melchert, C.,Behl, M.,Lendlein, A. %D 2011 %J Photonik %N 5 %P 77 %T Lichtinduzierte Formaenderung in Polymeren %U 5 %X Photosensitive Formänderungs- und Formgedächtnis-Materialien reagieren auf Belichtung mit einer Veränderung ihrer vorgegebenen Form, die mittels einer Polymermatrix von der molekularen Nano-Skala auf die Makro-Ebene übersetzt wird. Damit ergeben sich vielversprechende Funktionsmaterialien z.B. für optische Sensoren und Aktoren von Mikrorobotern, optische Mikropinzetten oder Pumpen. Ausgehend von den molekularen Grundlagen erläutern wir Funktion, Eigenschaften und Anwendungen. %0 journal article %@ 0391-3988 %A Feng, Y.,Lu, J.,Behl, M.,Lendlein, A. %D 2011 %J The International Journal of Artificial Organs %N 2 %P 103-109 %R doi:10.5301/IJAO.2011.6402 %T Degradable depsipeptide-based multiblock copolymers with polyester or polyetherester segments %U https://doi.org/10.5301/IJAO.2011.6402 2 %X Polydepsipeptides, alternating copolymers of an a-amino acid and a a-hydroxy acid, are an interesting group of degradable polymers. They have gained attention as potential degradable implant materials. Polydepsipeptides are expected to have better biocompatibility in vivo during the degradation process than aliphatic polyesters. Various depsipeptide-based polymers with or without pendant functional groups have been synthesized via ring-opening polymerization of corresponding morpholine-2,5-dione derivatives. The different polymer architectures of the polymers, for example, providing an alternating, random, diblock, triblock, or multiblock structure, can be obtained by appropriate selection of the polymerization reaction, which may be ring-opening or polyaddition. Recently, we synthesized thermoplastic phase-segregated copolymers with a multiblock structure containing polydepsipeptides and poly(e-caprolactone) or poly(p-dioxanone) segments via coupling of the respective diols using an aliphatic diisocyanate. The obtained multiblock copolymers showed good elastic properties at 25°C and 75°C. Furthermore, they exhibited a shape-memory capability. Here, we summarize the synthesis, biodegradation behavior and shape-memory properties of the multiblock copolymers. In addition, we introduce new combinations of depsipeptide/poly(ether)ester segments in multiblock copolymers. The depsipeptide-based multiblock copolymers have potential applications as biomaterials for controlled drug release, tissue engineering scaffolds, or base materials for biofunctional implants. %0 book part %@ %A Behl, M.,Zotzmann, J.,Schroeter, M.,Lendlein, A. %D 2011 %J Handbook of Biodegradable Polymers: Synthesis, Characterization and Applications %N %P 195-215 %T Biodegradable Shape-Memory Polymers %U %X %0 conference lecture %@ %A Melchert, C.,Behl, M.,Lendlein, A. %D 2011 %J MRS Fall 2011 Meeting %N %P %T Phase Transition Behavior of Main Chain Nematic Liquid-Crystalline Polymers Based on 2-methyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone and 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone %U %X %0 conference lecture (invited) %@ %A Behl, M.,Zotzmann, J.,Kratz, K.,Feng, Y.,Lendlein, A. %D 2011 %J Vortrag at the Hong Kong Polytechnic University, Institute of Textiles and Clothing %N %P %T Triple-Shape Polymers %U %X %0 journal article %@ 0957-4530 %A Zotzmann, J.,Ziegler, H.-J.,Behl, M.,Zierke, M.,Radke, W.,Lendlein, A. %D 2011 %J Journal of Materials Science: Materials in Medicine %N 10 %P 2147-2154 %R doi:10.1007/s10856-011-4404-6 %T Upscaling the synthesis of biodegradable multiblock copolymers capable of a shape-memory effect %U https://doi.org/10.1007/s10856-011-4404-6 10 %X Thermoplastic, phase-segregated multiblock copolymers (MBC) with shape–memory capability consisting of poly(ε-caprolactone) (PCL) switching segments and poly(p-dioxanone) (PDO) or poly(ω-pentadecalactone) (PPD) hard segments were prepared on a scale of several kilograms following a newly developed upscaling procedure. Dihydroxytelechelic poly(ether)esters were coupled by an aliphatic diisocyanate gaining products of sufficiently high molecular weights. The obtained biodegradable MBC exhibited good elastic properties and a shape–memory effect (SME) with a switching temperature (Tsw) around body temperature. The yield of the synthesis could be improved and reaction time reduced, while mechanical and shape–memory properties were not affected. These multifunctional materials, which are now available in a larger scale have a high application potential as smart implant materials especially for minimally invasive surgery. %0 conference poster %@ %A Behl, M.,Hiebl, B.,Feng, Y.,Lendlein, A. %D 2011 %J 13th CAST Annual Meeting, International Forum on Green Chemical Science & Engineering %N %P %T Biocompatibility of Degradable Shape-Memory Multiblock Copolymers with Polydepsipeptide- and Poly(ε-caprolactone)segments in vitro %U %X %0 conference lecture %@ %A Razzaq, M.Y.,Behl, M.,Lendlein, A. %D 2011 %J MRS Fall 2011 Meeting %N %P %T Shape-Memory Properties of Nanocomposites based on Poly(Omega-pentadecalactone) and Magnetic Nanoparticles %U %X %0 conference lecture %@ %A Zotzmann, J.,Behl, M.,Lendlein, A. %D 2011 %J MRS Fall 2011 Meeting, Symposium V %N %P %T Triple-Shape Effect of Copolymer Networks Based on Poly(Omega-pentadecalactone) and Poly(Epsilon-caprolactone) Segments Applying a Programming Procedure with an Adjusted Temperature Profile %U %X %0 conference poster %@ %A Iqbal, D.,Melchert, C.,Behl, M.,Lendlein, A.,Beuermann, S. %D 2011 %J MRS Fall 2011 Meeting %N %P %T Modeling of Free Radical Polymerization of Azobenzene-based Linear Polymers %U %X %0 conference poster %@ %A Yang, D.,Feng, Y.,Behl, M.,Lendlein, A.,Zhao, H.,Khan, M.,Guo, J. %D 2011 %J MRS Fall 2011 Meeting %N %P %T Biomimetic Hemo-compatible Surfaces of Polyurethane Obtained by PEG and MPC Grafted Copolymer Brushes %U %X %0 conference poster %@ %A Behl, M.,Zotzmann, J.,Lendlein, A. %D 2011 %J Advanced Functional Polymers for Medicine, AFPM 2011 %N %P %T The Influence of Programming Conditions on Triple-Shape Materials Based on Copolymer Networks With Two Crystallizable Switching Segments of Poly(w-pentadecalactone) and Poly(ε-caprolactone) %U %X %0 journal article %@ 1022-1360 %A Zotzmann, J.,Behl, M.,Lendlein, A. %D 2011 %J Macromolecular Symposia %N 1 %P 147-153 %R doi:10.1002/masy.201100039 %T The Influence of Programming Conditions on the Triple-Shape Effect of Copolymer Networks with Poly(Omega-pentadecalactone) and Poly(Epsilon-caprolactone) as Switching Segments %U https://doi.org/10.1002/masy.201100039 1 %X A versatile triple-shape material based on the two crystallizable segments poly(ω–pentadecalactone) and poly(ε-caprolactone) was synthesized showing triple-shape capability after application of the typical two-step triple-shape creation procedure at elevated temperatures (TSCP) as well as a one-step programming procedure at high temperature or at room temperature by cold drawing. By applying TSCP and varying the sequence of programming temperatures, the influence of the programming procedure on the triple-shape capability was investigated. The application of such a modified TSCP enabled to a certain extent the control of triple-shape capability by influencing the crystallization behavior of the two switching segments in these copolymer networks. %0 journal article %@ 0935-9648 %A Zotzmann, J.,Behl, M.,Hofmann, D.,Lendlein, A. %D 2010 %J Advanced Materials %N 31 %P 3424-3429 %R doi:10.1002/adma.200904202 %T Reversible Triple-Shape Effect of Polymer Networks Containing Polypentadecalactone- and Poly(Epsilon-caprolactone)-Segments %U https://doi.org/10.1002/adma.200904202 31 %X A reversible triple-shape effect is achieved for multi-phase polymer networks based on two different crystallizable segments. The reversibility of the two shape-changes is based on crystallization induced elongation (CIE) occurring during cooling and melting-induced contraction (MIC) during heating under constant stress. %0 journal article %@ 1743-4440 %A Lendlein, A.,Behl, M.,Hiebl, B.,Wischke, C. %D 2010 %J Expert Review of Medical Devices %N 3 %P 357-379 %R doi:10.1586/ERD.10.8 %T Shape-memory polymers as a technology platform for biomedical applications %U https://doi.org/10.1586/ERD.10.8 3 %X Polymeric materials are clinically required for medical devices, as well as controlled drug delivery systems. Depending on the application, the polymer has to provide suitable functionalities, for example, mechanical functions or the capability to actively move, so that an implant can be inserted in a compact shape through key-hole incisions and unfold to its functional shape in the body. Shape-memory polymers, as described herein regarding their general principle, compositions and architectures, have developed to a technology platform that allows the tailored design of such multifunctionality. In this way, defined movements of implants triggered either directly or indirectly, tailored mechanical properties, capability for sterilization, biodegradability, biocompatibility and controlled drug release can be realized. This comprehensive review of the scientific and patent literature illustrates that this technology enables the development of novel medical devices that will be clinically evaluated in the near future. %0 journal article %@ 0935-9648 %A Behl, M.,Razzaq, M.Y.,Lendlein, A. %D 2010 %J Advanced Materials %N 31 %P 3388-3410 %R doi:10.1002/adma.200904447 %T Multifunctional Shape-memory Polymers %U https://doi.org/10.1002/adma.200904447 31 %X The thermally-induced shape-memory effect (SME) is the capability of a material to change its shape in a predefined way in response to heat. In shape-memory polymers (SMP) this shape change is the entropy-driven recovery of a mechanical deformation, which was obtained before by application of external stress and was temporarily fixed by formation of physical crosslinks. The high technological significance of SMP becomes apparent in many established products (e.g., packaging materials, assembling devices, textiles, and membranes) and the broad SMP development activities in the field of biomedical as well as aerospace applications (e.g., medical devices or morphing structures for aerospace vehicles). Inspired by the complex and diverse requirements of these applications fundamental research is aiming at multifunctional SMP, in which SME is combined with additional functions and is proceeding rapidly. In this review different concepts for the creation of multifunctionality are derived from the various polymer network architectures of thermally-induced SMP. Multimaterial systems, such as nanocomposites, are described as well as one-component polymer systems, in which independent functions are integrated. Future challenges will be to transfer the concept of multifunctionality to other emerging shape-memory technologies like light-sensitive SMP, reversible shape changing effects or triple-shape polymers. %0 book part %@ %A Behl, M.,Zotzmann, J.,Lendlein, A. %D 2010 %J Advances in Polymer Science - Shape-memory Polymers %N %P 1-40 %R doi:10.1007/12_2009_26 %T Shape-Memory Polymers and Shape-Changing Polymers %U https://doi.org/10.1007/12_2009_26 %X The ability of polymers to respond to external stimuli is of high scientific and technological significance. In the last few years, research activities have been intensified substantially, exploring whether stimuli-sensitive polymers can be designed that move actively. In this review actively-moving materials were classified according to the underlying mechanisms enabling the shape changes: shape-memory polymers and shape-changing polymers / shape-changing gels were identified. The application spectra of these materials as well as the current developments were elucidated and general molecular design principles presented. When applicable, a further distinction according to the applied stimulus was made. %0 journal article %@ 0959-9428 %A Behl, M.,Lendlein, A. %D 2010 %J Journal of Materials Chemistry %N %P 3335-3345 %R doi:10.1039/b922992b %T Triple-shape polymers %U https://doi.org/10.1039/b922992b %X Shape-memory polymers (SMPs) are an emerging class of active materials, which are able to change their shape in a predefined way upon appropriate stimulation. As SMPs can switch from a temporary to their permanent shape they are dual-shape materials. Recently, multiphase polymer networks were explored, which are able to switch from a first shape (A) to a second shape (B) and from there to a third shape (C). Here we highlight this triple-shape effect (TSE) as a thermally triggered effect. The generality of the concept will be explained by describing suitable polymer network architectures and appropriate triple-shape creation processes (TSCPs). TSCP is a thermomechanical treatment typically consisting of two consecutive deformation steps resulting in shapes B and A. The molecular architecture of triple-shape polymers (TSPs) also contains the essential elements for the dual-shape effect (DSE), which therefore was systematically investigated. The understanding of the underlying mechanisms recently led to the discovery of a system, where a thermomechanical treatment with only one single deformation step resulted in a TSE. TSPs enable complex, active deformations on demand, having a high potential as enabling technology for application fields including intelligent medical devices, textile and assembling systems. %0 conference lecture %@ %A Lendlein, A.,Kratz, K.,Hiebl, B.,Behl, M. %D 2010 %J Makromolekulares Kolloquium %N %P %T Active Biomaterials %U %X %0 conference poster %@ %A Radke, W.,N´Goma, P.Y.,Ziegler, H.-J.,Zierke, M.,Behl, M.,Lendlein, A. %D 2010 %J Biodegradable Polymers as Biomaterials, 459th WE-Heraeus-Seminar %N %P %T Characterization of Multiblockcopolymers by Chromatographic Techniques %U %X %0 conference poster %@ %A Behl, M.,Zotzmann, J.,Lendlein, A. %D 2010 %J Biodegradable Polymers as Biomaterials, 459th WE-Heraeus-Seminar %N %P %T Shape-Memory and Reversible Dual-Shape Effect of Polymer Networks Based on Polypentadecalactone Segments %U %X %0 conference poster %@ %A Pierce, B.,Bellin, K.,Behl, M.,Lendlein, A. %D 2010 %J Biodegradable Polymers as Biomaterials, 459th WE-Heraeus-Seminar %N %P %T Solvent- and Thermally-Induced Shape-Memory Effect of Polymer Networks Based on Poly[(rac-lactide)-co-glycolide] %U %X %0 book part %@ %A Behl, M.,Lendlein, A. %D 2010 %J Shape-Memory Polymers and Multifunctional Composites %N %P 1-20 %T Overview of Shape-memory Polymers %U %X The ability of polymers to respond to external stimuli such as heat or light is of high scientific and technological significance. Their stimuli-sensitive behavior enables such materials to change certain macroscopic properties such as shape, color or refractive index controlled by an external signal. The implementation of the capability to actively move into polymers has attracted researcher’s interest, especially in the last years, and was achieved in polymers as well as gels. Sensitivity to heat, light, magnetic fields, ion strength or pH value was realized in gels [1]. In non-swollen polymers active movement is stimulated by exposition to heat or,light and could also be designed as a complex movement with more than two shapes.,Besides their scientific significance such materials have an high innovation potential and can be found e.g. in smart fabrics [2-4], heat-shrinkable tubes for electronics or films for packaging [5], self-deployable sun sails in space crafts [6], self-disassembling mobile phones,[7], intelligent medical devices [8] or implants for minimally invasive surgery [9-11]. These enumerations are only exemplarily and cover only a small amount of potential applications. Actively moving polymers may even reshape product design [12]. In this chapter different,classes of actively moving materials are introduced with an emphasis on shape-memory polymers. The fundamental principles of the different functions are explained and examples for specific materials are given. %0 conference paper %@ %A Lendlein, A.,Behl, M.,Kamlage, S. %D 2010 %J Advances in Regenerative Medicine: Role of Nanotechnology, and Engineering Principles, NATO Science for Peace and Security Series A: Chemistry and Biology, Proceedings of the NATO Advanced Research Workshop on Nanoengineered Systems for Regenerative Medicine %N %P 131-156 %R doi:10.1007/978-90-481-8790-4 %T The Nature of the Thermal Transition Influences the Shape-Memory Behavior of Polymer Networks %U https://doi.org/10.1007/978-90-481-8790-4 %X The contributions to this book, all written by leading experts in their respective disciplines, describe and explore the various facets of regenerative medicine and highlight the role of the "the nano length scale" and of "nano-scale systems" in defining and controlling cell and tissue environments. The development of novel tissue-regeneration strategies requires the integration of new insights emerging from studies of cell-matrix interactions, cellular signalling processes, and developmental and systems biology, into biomaterials design, ideally via a systems approach. The chapters cover a wide spectrum of topics ranging from stem cell biology, developmental biology, cell-matrix interactions, and matrix biology to surface science, materials processing and drug delivery. The book will be an especially valuable resource for researchers developing regenerative medicine paradigms that combine these facets into clinically translatable solutions. %0 conference lecture %@ %A Behl, M.,Lendlein, A. %D 2010 %J German-Thai Symposium on Nanoscience and Nanotechnology %N %P %T Biomaterials for Regenerative Medicine %U %X %0 journal article %@ 1616-5187 %A Feng, Y.,Lu, J.,Behl, M.,Lendlein, A. %D 2010 %J Macromolecular Bioscience %N 9 %P 1008-1021 %R doi:10.1002/mabi.201000076 %T Progress in Depsipeptide-Based Biomaterials %U https://doi.org/10.1002/mabi.201000076 9 %X Polydepsipeptides – alternating copolymers of an α-amino acid and an α-hydroxy acid – are a group of biodegradable polymers. Versatile polydepsipeptides with or without pendant functional groups, as well as various polymer architectures, for example, providing alternative, random, diblock, triblock, multiblock or graft sequence structures, can be synthesized via ring-opening copolymerization of various morpholine-2,5-dione derivatives. They are potential candidates for a wide range of biomedical applications. Polydepsipeptides are described in this review from the aspect of materials science, especially as biomaterials. We mainly focus on various techniques developed to synthesize polydepsipeptides and their copolymers, biodegradation behaviors, shape-memory properties and possible biomedical applications. %0 conference poster %@ %A Lu, J.,Feng, Y.,Behl, M.,Lendlein, A. %D 2010 %J Biodegradable Polymers as Biomaterials, 459th WE-Heraeus-Seminar %N %P %T Biodegradable Depsipeptide-based Biomaterials %U %X %0 conference lecture (invited) %@ %A Behl, M.,Feng, Y.,Zotzmann, J.,Lendlein, A. %D 2010 %J Trilateral Symposium on NanoBio Integration %N %P %T Degradable Shape-memory Polymers %U %X %0 conference lecture (invited) %@ %A Lendlein, A.,Behl, M. %D 2010 %J 14th International Scientific Conference on Polymeric Materials %N %P %T Actively Moving Polymers %U %X %0 journal article %@ 1359-7345 %A Kummerloewe, G.,Behl, M.,Lendlein, A.,Luy, B. %D 2010 %J Chemical Communications : ChemComm %N 43 %P 8273-8275 %R doi:10.1039/C0CC02730H %T Artifact-free measurement of residual dipolar couplings in DMSO by the use of cross-linked perdeuterated poly(acrylonitrile) as alignment medium %U https://doi.org/10.1039/C0CC02730H 43 %X Perdeuterated poly(acrylonitrile) is introduced as a practically proton-free alignment medium for the measurement of anisotropic NMR parameters; its use in conventional glass tubes and in a Kalrez® 8002 UP-based stretching device with resulting spectra of astonishing quality are demonstrated. %0 journal article %@ 1616-301X %A Zotzmann, J.,Behl, M.,Feng, Y.,Lendlein, A. %D 2010 %J Advanced Functional Materials %N 20 %P 3583-3594 %R doi:10.1002/adfm.201000478 %T Copolymer Networks Based on Poly(Omega-pentadecalactone) and Poly(Epsilon-caprolactone)Segments as a Versatile Triple-Shape Polymer System %U https://doi.org/10.1002/adfm.201000478 20 %X Thermo-sensitive triple-shape polymers can perform two consecutive shape changes in response to heat. These shape changes correspond to the recovery of two different deformations in reverse order, which were programmed previously at elevated temperature levels (Tmid and Thigh) by the application of external stress. Recently, an AB copolymer network was described, which surprisingly exhibited a triple-shape effect despite being programmed with only one deformation at Thigh. Here it is explored whether a copolymer network system can be designed that enables a one-step deformation process at ambient temperature (cold drawing) as a novel, gentle, and easy-to-handle triple-shape-creation procedure, in addition to the procedures reported to date, which generally involve deformation(s) at elevated temperature(s). A copolymer-network system with two crystallizable polyester segments is synthesized and characterized, fulfilling two crucial criteria. These materials can be deformed at ambient temperature by cold drawing and show, even at Thigh, which is above the melting points of both switching domains, elongation at break of up to 250%. Copolymer networks with PCL contents of 75 and 50 wt% show a triple-shape effect after cold drawing with shape-fixity ratios between 65% and 80% and a total-shape-recovery ratio above 97%. Furthermore, in these copolymer networks, the triple-shape effect can be obtained after a one-step deformation at Thigh. Independent of the temperature at which the deformation is applied (ambient temperature or Thigh), copolymer networks that have the same compositions show similar switching temperatures and proportioning of the recovery in two steps. The two-step programming procedure enables a triple-shape effect in copolymer networks for an even broader range of compositions. This versatile triple-shape-material system based on tailored building blocks is an interesting candidate material for applications in fixation systems or disassembling systems. %0 journal article %@ 0959-9428 %A Kumar, U.N.,Kratz, K.,Wagermaier, W.,Behl, M.,Lendlein, A. %D 2010 %J Journal of Materials Chemistry %N 17 %P 3404-3415 %R doi:10.1039/b923000a %T Non-contact actuation of triple-shape effect in multiphase polymer network nanocomposites in alternating magnetic field %U https://doi.org/10.1039/b923000a 17 %X Triple-shape polymers (TSP) can memorize two independent shapes, which are recovered when the temperature is subsequently increased. Certain applications do not allow triggering of the triple-shape effect (TSE) by environmental heating (e.g. potential damaging of surrounding tissue) and therefore require a non-contact activation. Here we explored whether polymer nanocomposites can be designed, which enable non-contact activation of TSE in an alternating magnetic field. %0 conference paper %@ %A Lendlein, A.,Behl, M. %D 2010 %J Medical Device Materials V, Proceedings from the Materials Processes for Medical Devices Conference, MPMD 2009 %N %P 100-104 %T Active Biomaterials %U %X %0 conference lecture (invited) %@ %A Zotzmann, J.,Kelch, S.,Alteheld, A.,Behl, M.,Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %N %P %T Ability to Control the Glass Transition Temperature of Amorphous Shape-Memory Polyesterurethane Networks by Varying Prepolymers in Molecular Mass as well as in Type and Content of Incorporated Comonomers %U %X %0 journal article %@ 1744-683X %A Behl, M.,Ridder, U.,Feng, Y.,Kelch, S.,Lendlein, A. %D 2009 %J Soft Matter %N 3 %P 676-684 %R doi:10.1039/b810583a %T Shape-memory capability of binary multiblock copolymer blends with hard and switching domains provided by different components %U https://doi.org/10.1039/b810583a 3 %X The structural concept of shape-memory polymers (SMP) is based on two key components: covalent or physical crosslinks (hard domains) determining the permanent shape and switching domains fixing the temporary shape as well as determining the switching temperature Tsw. In conventional thermoplastic SMP hard and switching domains determining segments are combined in one macromolecule. In this paper we report on binary polymer blends from two different multiblock copolymers, whereby the first one provides the segments forming hard domains and the second one the segments forming the switching domains. A poly(alkylene adipate) mediator segment is incorporated in both multiblock copolymers to promote their miscibility as the hard segment poly(p-dioxanone) (PPDO) and the switching segment poly(-caprolactone) (PCL) are non-miscible. All polymer blends investigated showed excellent shape-memory properties. The melting point associated to the PCL switching domains Tm,PCL is almost independent of the weight ratio of the two blend components. At the same time the mechanical properties can be varied systematically. In this way complex synthesis of new materials can be avoided. Its biodegradability, the variability of mechanical properties and a Tsw around body temperature are making this binary blend system an economically efficient, suitable candidate for diverse biomedical applications. %0 journal article %@ 1616-5187 %A Feng, Y.,Behl, M.,Kelch, S.,Lendlein, A. %D 2009 %J Macromolecular Bioscience %N 1 %P 45-54 %R doi:10.1002/mabi.200800199 %T Biodegradable Multiblock Copolymers Based on Oligodepsipeptides with Shape-Memory Properties %U https://doi.org/10.1002/mabi.200800199 1 %X Thermoplastic phase-segregated multiblock copolymers with polydepsipeptides and PCL segments were prepared via coupling of diol and PCL-diol using an aliphatic diisocyanate. The obtained multiblock copolymers showed good elastic properties and a shape memory. Almost complete fixation of the mechanical deformation, resulting in quantitative recovery of the permanent shape with a switching temperature around body temperature, was observed. In hydrolytic degradation experiments, a quick decrease of the molecular weight without induction period was observed, and the material changed from elastic to brittle in 21 d. These materials promise a high potential for biomedical applications such as smart implants or medical devices. %0 journal article %@ 0957-4530 %A Zotzmann, J.,Alteheld, A.,Behl, M.,Lendlein, A. %D 2009 %J Journal of Materials Science: Materials in Medicine %N 9 %P 1815-1824 %R doi:10.1007/s10856-009-3761-x %T Amorphous phase-segregated copoly(ether)esterurethane thermoset networks with oligo(propylene glycol) and oligo[(rac-lactide)-co-glycolide] segments: synthesis and characterization %U https://doi.org/10.1007/s10856-009-3761-x 9 %X Completely amorphous copoly(ether)ester networks based on oligo(propylene glycol) and oligo[(rac-dilactide)-co-glycolide] segments were synthesized by crosslinking star-shaped hydroxyl-telechelic cooligomers using an aliphatic low-molecular weight diisocyanate. Two different network architectures were applied exhibiting differences in the phase-separation behavior. For networks from oligo(propylene glycol)-block-oligo[(rac-lactide)-co-glycolide] triols (G3OPG-bl-OLG) only one glass transition was obtained. However, networks from a mixture of oligo(propylene glycol) triols (G3OPG) and oligo[(rac-lactide)-co-glycolide] tetrols (P4OLG) with a ratio of components in a certain range show two glass transition temperatures (T g) being attributed to two segregated amorphous phases. In this way a wide spectrum of mechanical properties can be realized and adjusted to the requirements of a specific application. %0 journal article %@ 1616-301X %A Behl, M.,Bellin, I.,Kelch, S.,Wagermaier, W.,Lendlein, A. %D 2009 %J Advanced Functional Materials %N 1 %P 102-108 %R doi:10.1002/adfm.200800850 %T One-Step Process for Creating Triple-Shape Capability of AB Polymer Networks %U https://doi.org/10.1002/adfm.200800850 1 %X Triple-shape polymers can move from a first shape (A) to a second shape (B) and from there to a third shape (C), where both shape changes are induced by temperature increases. This triple-shape capability is obtained for multiphase polymer networks after application of a complex thermomechanical programming process, which consists of two steps; these steps create shapes (B) and (A), while shape (C) is defined by the covalent crosslinks of the polymer network. Here, the creation of the triple-shape capability for an AB polymer network system by a simple one-step process similar to a conventional dual-shape programming process is reported. The polymer networks are based on poly(-caprolactone) (PCL) and poly(cyclohexyl methacrylate); favorable compositions for obtaining a triple shape effect have a PCL content between 35 and 60 wt%. This finding substantially facilitates handling of the triple-shape technology and is an important step toward the realization of potential applications in which more than one shape change is required. %0 conference lecture (invited) %@ %A Kelch, S.,Behl, M.,Kamlage, S.,Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %N %P %T Multiphase Polymer Networks with Shape-Memory %U %X %0 conference lecture (invited) %@ %A Behl, M.,Ridder, U.,Kelch, S.,Wagermaier, W.,Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %N %P %T Mechanical Properties of Polymer Blends Having Shape-memory Capability %U %X %0 conference paper %@ %A Razzaq, M.Y.,Behl, M.,Kratz, K.,Lendlein, A. %D 2009 %J Advances in Material Design for Regenerative Medicine, Drug Delivery, and Targeting/Imaging, MRS Symposium Proceedings, MRS Fall Meeting 2008 %N %P HH05-07 %R doi:10.1557/PROC-1140-HH05-07 %T Controlled Actuation of Shape-Memory nanocomposites by Application of an Alternating Magnetic Field %U https://doi.org/10.1557/PROC-1140-HH05-07 %X %0 conference lecture (invited) %@ %A Lendlein, A.,Behl, M. %D 2009 %J Materials Processes for Medical Devices Conference, MPMD 2009 %N %P %T Active Biomaterials %U %X %0 conference paper %@ %A Kumar, U.N.,Kratz, K.,Behl, M.,Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %N %P NN03-21 %R doi:10.1557/PROC-1190-NN03-21 %T Triple-Shape Capability of Thermo-Sensitive Nanocomposites from Multiphase Polymer Networks and Magnetic Nanoparticles %U https://doi.org/10.1557/PROC-1190-NN03-21 %X %0 conference paper %@ %A Kelch, S.,Behl, M.,Kamlage, S.,Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %N %P NN01-06 %T Multiphase Polymer Networks with Shape-Memory %U %X %0 conference paper %@ %A Behl, M.,Ridder, U.,Kelch, S.,Wagermaier, W.,Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %N %P NN01-05 %T Mechanical Properties of Polymer Blends Having Shape-memory Capability %U %X %0 conference lecture %@ %A Wagermaier, W.,Hofmann, D.,Kratz, K.,Behl, M.,Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %N %P %T X-ray Scattering Studies to Investigate Triple-shape Capability of Polymer Networks Based on poly(?-caprolactone) and poly(cyclohexyl methacrylate) Segments %U %X %0 conference paper %@ %A Wagermaier, W.,Hofmann, D.,Kratz, K.,Behl, M.,Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %N %P NN03-18 %R doi:10.1557/PROC-1190-NN03-18 %T X-ray Scattering Studies to Investigate Triple-shape Capability of Polymer Networks Based on poly(?-caprolactone) and poly(cyclohexyl methacrylate) Segments %U https://doi.org/10.1557/PROC-1190-NN03-18 %X %0 conference paper %@ %A Zotzmann, J.,Kelch, S.,Alteheld, A.,Behl, M.,Lendlein, A. %D 2009 %J Active Polymers - MRS Symposium Proceedings, MRS Spring Meeting 2009 %N %P NN01-09 %R doi:10.1557/PROC-1190-NN01-09 %T Ability to Control the Glass Transition Temperature of Amorphous Shape-Memory Polyesterurethane Networks by Varying Prepolymers in Molecular Mass as well as in Type and Content of Incorporated Comonomers %U https://doi.org/10.1557/PROC-1190-NN01-09 %X %0 conference lecture %@ %A Kumar, U.N.,Kratz, K.,Behl, M.,Lendlein, A. %D 2009 %J MRS Spring Meeting 2009 %N %P %T Triple-Shape Capability of Thermo-Sensitive Nanocomposites from Multiphase Polymer Networks and Magnetic Nanoparticles %U %X %0 conference lecture %@ %A Behl, M.,Lendlein, A. %D 2008 %J 3rd International Conference on Nanotechnology and Textiles %N %P %T Shape-Memory Polymers %U %X %0 book part %@ %A Behl, M.,Langer, R.,Lendlein, A. %D 2008 %J Intelligent Materials, Chapter 12 %N %P 301-316 %T Intelligent Materials: Shape-Memory Polymers %U %X %0 book part %@ %A Behl, M.,Lendlein, A. %D 2008 %J Yearbook Of Science & Technology 2008 %N %P 293-296 %T Shape-Memory Polymers %U %X Shape-memory polymers are an emerging class of active polymers which can change their shape in a predefined way when exposed to an appropriate stimulus. Shape-memory research was initialized by the development of thermo-sensitive materials. These materials had a dual shape capability as they could move from a first to a second shape. This concept was extended to other stimuli by either indirect thermal actuation or direct actuation by addressing stimuli-sensitive functional groups on the molecular level. Recently, triple shape materials were introduced, which can perform two shape changes after subsequent temperature increases. In this paper fundamental aspects of the molecular design of suitable polymer architectures, tailored creation of the different shapes and the quantification of the dual as well as the triple shape effect are presented. %0 conference lecture (invited) %@ %A Lendlein, A.,Behl, M. %D 2008 %J 3rd International Conference Smart Materials, Structures and Systems %N %P %T Shape-Memory Polymers for Biomedical Applications %U %X %0 conference poster %@ %A Zotzmann, J.,Behl, M.,Kelch, S.,Choi, N.-Y.,Lendlein, A. %D 2008 %J Tag der Chemie, VCI Berlin Brandenburg %N %P %T Multifunctional Polymer Networks from Poly(rac-lactide)-b-poly(propylene oxide)-b-poly(rac-lactide) dimethacrylates %U %X %0 conference poster %@ %A Razzaq, M.,Behl, M.,Lendlein, A. %D 2008 %J Polydays 2008 %N %P %T Effect of Magnetic Nanoparticles on Thermal and Mechanical Properties of Shape-Memory Polymer Networks %U %X %0 conference lecture (invited) %@ %A Lendlein, A.,Franke, R.-P.,Jung, F.,Behl, M. %D 2008 %J Lenkungsausschusssitzung HGF %N %P %T Program Regenerative Medicine %U %X %0 book part %@ %A Bellin, K.,Behl, M.,Lendlein, A. %D 2008 %J Aktuelles aus der Klinischen Haemorheologie und Mikrozirkulation %N %P 15-17 %T Massschneidern von Eigenschaften und Funktionen von Polymeren fuer Anwendungen in der Medizin %U %X %0 journal article %@ 1662-0356 %A Lendlein, A.,Behl, M. %D 2008 %J Advances in Science and Technology, Smart Materials & Micro/Nanosystems %N %P 96-102 %R doi:10.4028/www.scientific.net/AST.54.96 %T Shape-memory Polymers for Biomedical Applications %U https://doi.org/10.4028/www.scientific.net/AST.54.96 %X Most polymers used in clinical applications today are materials that have been developed originally for application areas other than biomedicine. On the other side, different biomedical applications are demanding different combinations of material properties and functionalities. Compared to the intrinsic material properties, a functionality is not given by nature but result from the combination of the polymer architecture and a suitable process. Examples for functionalities that play a prominent role in the development of multifunctional polymers for medical applications are biofunctionality (e.g. cell or tissue specificity), degradability, or shape-memory functionality. In this sense, an important aim for developing multifunctional polymers is tailoring of biomaterials for specific biomedical applications. Here the traditional approach, which is designing a single new homo- or copolymer, reaches its limits. The strategy, that is applied here, is the development of polymer systems whose macroscopic properties can be tailored over a wide range by variation of molecular parameters.,The Shape-memory capability of a material is its ability to trigger a predefined shape change by exposure to an external stimulus. A change in shape initiated by heat is called thermally-induced shape-memory effect. Thermally, light-, and magnetically induced shape-memory polymers will be presented, that were developed especially for minimally invasive surgery and other biomedical,applications. Furthermore triple-shape polymers will be introduced, that have the capability to perform two subsequent shape changes. Thus enabling more complex movements of a polymeric material. %0 conference lecture %@ %A Behl, M.,Bellin, I.,Kelch, S.,Wagermaier, W.,Lendlein, A. %D 2008 %J MRS Fall Meeting 2008, Symposium HH, Advances in Material Design for Regenerative Medicine, Drug Delivery, and Targeting/Imaging %N %P %T Dual and Triple Shape Capability of AB Polymer Networks based on Poly(Epsilon-caprolactone)dimethacrylates %U %X %0 conference lecture %@ %A Behl, M.,Lendlein, A. %D 2008 %J Vortrag DFG-SPP 1420-Projekt %N %P %T Hierarchically structuring multiphase polymer networks in layer systems for enabling thermally-triggered complex shape changes %U %X %0 conference paper %@ %A Behl, M.,Bellin, I.,Lelch, S.,Wagermaier, W.,Lendlein, A. %D 2008 %J Advances in Material Design for Regenerative Medicine, Drug Delivery, and Targeting/Imaging, MRS Symposium Proceedings, MRS Fall Meeting 2008 %N %P HH01-02 %R doi:10.1557/PROC-1140-HH01-02 %T Dual and Triple Shape Capability of AB Polymer Networks based on Poly(e-caprolactone)dimethacrylates %U https://doi.org/10.1557/PROC-1140-HH01-02 %X %0 conference lecture %@ %A Razzaq, M.Y.,Behl, M.,Kratz, K.,Lendlein, A. %D 2008 %J MRS Fall Meeting 2008, Symposium HH, Advances in Material Design for Regenerative Medicine, Drug Delivery, and Targeting/Imaging %N %P %T Controlled Actuation of Shape-Memory nanocomposites by Application of an Alternating Magnetic Field %U %X %0 journal article %@ 1369-7021 %A Behl, M.,Lendlein, A. %D 2007 %J Materials Today %N 4 %P 20-28 %R doi:10.1016/S1369-7021(07)70047-0 %T Shape Memory Polymers %U https://doi.org/10.1016/S1369-7021(07)70047-0 4 %X Shape-memory polymers are an emerging class of active polymers that have dual-shape capability. They can change their shape in a predefined way from shape A to shape B when exposed to an appropriate stimulus. While shape B is given by the initial processing step, shape A is determined by applying a process called programming. We review fundamental aspects of the molecular design of suitable polymer,architectures, tailored programming and recovery processes, and the,quantification of the shape-memory effect. Shape-memory research,was initially founded on the thermally induced dual-shape effect. This concept has been extended to other stimuli by either indirect thermal actuation or direct actuation by addressing stimuli-sensitive groups,on the molecular level. Finally, polymers are introduced that can,be multifunctional. Besides their dual-shape capability, these active materials are biofunctional or biodegradable. Potential applications for such materials as active medical devices are highlighted. %0 conference lecture %@ %A Lendlein, A.,Behl, M. %D 2007 %J BCRT- Retreat, Klausurtagung %N %P %T Field B: Bio- Engineering %U %X %0 conference lecture %@ %A Lendlein, A.,Behl, M.,Kamlage, S. %D 2007 %J NATO Advanced Research Workshop on Nanoengineered Systems for Regenerative Medicine %N %P %T The Nature of the Thermal Transition influences the Shape-memory Behavior of Polymer Networks %U %X %0 conference lecture (invited) %@ %A Lendlein, A.,Behl, M. %D 2007 %J NanoMat 8 Szene, Forschungszentrum Karlsruhe %N %P %T Actively Moving Polymers %U %X %0 journal article %@ 1744-683X %A Behl, M.,Lendlein, A. %D 2007 %J Soft Matter %N 1 %P 58-67 %R doi:10.1039/b610611k %T Actively Moving Polymers %U https://doi.org/10.1039/b610611k 1 %X The ability of polymers to move actively in response to an external stimulus such as heat or light is of high scientific and technological significance. In any instance stimuli-responsive effects on the molecular level are converted into macroscopic movement, whereby generally two different moving behaviors have to be differentiated for polymer-based materials: the shape-memory effect and the shape-changing capability. Basic concepts for the molecular design of suitable polymer architectures for shape-memory polymers as well as tailored programming processes are presented. The thermally-induced shape-memory effect of polymers is described as well as the extension of this concept to other stimuli than heat. Indirect actuation of the thermally-induced effect by IR-irradiation, electric current, humidity or alternating magnetic fields are outlined as well as recent work on light-induced shape-memory polymers. For shape-changing polymers, two basic concepts are presented: shape changes occurring during phase orientation of liquid crystal elastomers (LCE) and the photomechanical effect based on photoisomerization of moieties, such as azo-groups incorporated in suitable polymer systems.