Photo: Hereon/Christian Schmid
The department of “Microporous Polymers” focuses on the synthesis and characterisation of tailor-made microporous polymers. The development of new materials for membrane applications for filtration and gas separation is in the foreground. For certain applications, specifically novel monomers are developed. Nanoparticles are further functionalised, in order to achieve better dispersibility in a defined polymeric matrix.
The emphasis is in the anionic polymerisation and controlled radical polymerisation techniques. Besides various reactors, the department also has custom-made Schlenk lines to implement the synthesis. The monomers and polymers are characterised through various methods in the department.
Photo: Hereon/Christian Schmid
Image: Hereon/Volkan Filiz
The department of "Microporous Polymers" synthesises tailored polymers (homopolymers and copolymers) for all departments of the institute according to special requirements. In the copolymers, the different units can be statistically or alternately distributed, or they can exist in the form of blocks. Depending on the number of segments (of homopolymer blocks), the block copolymers can be distinguished in di-, tri-or multiblock copolymers.
Die Forschungsschwerpunkte unserer Abteilung:
The polymer Polyvinyltrimethylsilane (PVTMS) which was previously manufactured in the Soviet Union for the separation of nitrogen / oxygen is reesthablished in our department. This polymer has excellent properties in permeability and selectivity. In collaboration with the department of "Process Engineering" of the institute PVTMS membranes are currently used in a project for the nitrogen enrichment of the charge air for marine diesel engines to reduce emissions of nitrogen oxides. The aim is to improve the properties of the membrane and further to facilitate the workability of PVTMS to membranes.
Block copolymers are particularly promising for membrane applications for filtration and gas separation. The special feature of block copolymers is that they can form highly ordered structures by self-assembly of immiscible blocks.
Block copolymers consist of at least two types of monomer, which are each present as polymer blocks covalently linked together. The top layer of ultra-thin block copolymer membranes is highly ordered and uniformly permeated by pores. It acts as a filter and meets the separation tasks. The lower layer has a sponge-like structure and provides for stability. Different sized molecules, but also viruses and bacteria can be separated, which opens up applications in medicine.
A further advantage of these membranes is the potential of switchability what is currently being intensively researched. The suitable choice of the monomers results in the possibility of pH-dependent switchability of the pore size. Additional post functionalisation of the membrane also allows, for example, the temperature-dependent adjustment of the pore size.
The binding of bioactive molecules broadens the application spectrum of the block copolymer membranes. For this purpose, an appropriate functionalisation of end groups is required.
Glassy polymers with high intrinsic microporosity combine very high permeabilities with good selectivities. These polymers with high free volume can be used for a variety of membrane applications (nanofiltration, pervaporation, vapor and gas separation). The synthesis is carried out via a polycondensation. We aim at the synthesis of new monomers and the improvement of properties of the membrane by the addition of fillers to the polymer, especially with regard to the long term stability.
Commercial polymers for membranes for gas separation can be improved by nanoscale fillers in various properties, namely separation and permeability, and in the long term stability. Such mixed matrix membranes can also get additional properties, depending on the type of fillers. For example, we have used multi-walled carbon nanotubes as filler to produce an electrically conductive mixed matrix membrane for the separation of explosive gas mixtures, which is able to dissipate any static electricity.
The characterization of the membranes is in close cooperation with the Department of "Process Engineering".