The Coating Expert

Illustration: Hereon/ Bianca Seth, background: quniky - de.freepik.coma, portrait: Hereon/ Steffen Niemann

Juliana Clodt stands in front of a steel frame with various rolls, over which runs a fleece material measuring more than two hundred metres long and up to sixty centimetres wide. A portion of this setup consists of various tubes and a furnace warmed to one hundred degrees. “That’s it—our coating machine,” says the 37-year-old proudly. She’s been learning from her colleague Jan Wind for the last year and a half how to control the system. The engineer is soon retiring. A person must know, just as he does, every little screw on the apparatus—and Clodt is now getting very close. “The large machine instilled a great deal of respect in me at the beginning. I now know, however, very well which screws I need to turn to apply the different layers that give the membranes their desired properties,” she says.

“We receive the most varying inquiries from research institutions and from the industrial sector, for example, for flue gas separation.” The membranes are basically all structured the same: “We must initially produce the polymer solution that is poured inside the membrane casting machine on a fleece material. This fleece is then immersed in a water bath, whereby the membrane is precipitated and a porous structure is formed. The membrane is then cleaned and coated in three steps,” the scientist explains. “The washed membrane roll is clamped in the coating machine and we first apply a silicone-based drainage layer. Then comes the actual active separation layer. For the entire roll we only need seven grams of the polymer, from which this extremely thin layer (measuring fifty to one hundred nanometres in thickness) is produced. Then the topcoat follows, which is used to mechanically stabilise the membrane. The solution compositions and the machine settings during each step are vital for success. After every coating, the membrane rolls once through the furnace to dry and cross-link the polymer coating,” says Clodt. Depending on the requirements of the membrane, a different approach can be used to optimise the result. Sometimes it’s clear immediately what needs to be changed, but it is often a longer process.

“I need distance to be creative. The best ideas come to me when I’m doing something entirely different.”

“In 2012 we wanted to develop a membrane in which the pore size could be controlled by temperature as well as by the pH value. The question was how I could dock a molecule that reacts to temperature to a membrane that reacts to the pH value. The idea as to which chemical reaction I needed came to me when painting a balloon for a birthday party”—this resulted in her first scientific publication at the Hereon.

As a small child, Juliana Clodt wanted to work in agriculture or as a veterinarian—the desire seemed obvious, as she grew up on a farm near Unna. “But in school, I had already found chemistry fascinating—we undertook a great deal of practical work in the advanced course.” Following this path, she studied chemistry at the University of Münster, where she also earned her doctorate.

“I was especially enthralled by organic chemistry. It was always fun to discover how the molecules would react with each other.”

Clodt always had a special interest in the subject of polymer chemistry. “The postdoc position at the Hereon came in 2011, right on cue." Here she learned how to produce block copolymer membranes and she built a protein measurement stand. She has been working in the Process Engineering Department since 2016, where the chemist produces what are known as thin-film composite membranes for gas separation, currently for separating the greenhouse gas carbon dioxide. The mixture of writing and practical work in the membrane casting hall is the perfect fit for her.

During her PhD studies the chemist studied in Amsterdam for six months in 2009 within the framework of a “Graduiertekolleg“, an international research graduate programme. By then Clodt had noticed that she belonged in a big city. Today she lives with her family in Hamburg. She and her husband have been together prior to university, and today they have a son and a daughter. Something was clear to the couple: “We take care of the household, children and job on equal footing. We both work about thirty hours a week—the kids benefit from that.” It is also clear to the mother that profession and work remain separate. “When I’m off in the evening or on vacation, I’m usually unreachable. It wouldn’t work for me any other way.” In her free time, she likes to play guitar in her band. And while doing so, who knows what ideas might still come to Juliana Clodt concerning her work in polymer research.