Fraunhofer Institute for Interfacial Engineering and Biotechnology
Plasma glow discharge is a versatile tool especially suitable for the chemical surface modification of polymeric membranes. Using this technique, etching, (regioselective) functionalization or deposition of a thin film in the nanometer range is possible with only a very tiny consumption of precursor chemicals. In this way the pore size of asymmetric membranes can be influenced in a defined manner by etching or plasma polymerization to adjust the filtration characteristics or to create a closed pinhole-free thin film with an adjustable crosslink density to create a solvent-stable permselective layer for the separation of organic vapors or solvents.
At Fraunhofer IGB we have longstanding expertise in the handling of nanoparticle dispersions. We stabilize and functionalize such particles and, equipped with all the necessary infrastructure, characterize them by laser scattering or zetapotential measurements, for example. We use such dispersions to adjust the molecular weight cut-off of ceramic membranes coming from micro- to nanofiltration membranes. Or we disperse the particles in polymer solutions leading directly to mixed-matrix membranes with tailored properties.
Catalytically active membrane surfaces
We modify the surface of our membranes with noble metal precursors. After reductive sintering, membrane surfaces with a high catalytic activity are obtained. These systems can be used as membrane reactors e.g. for hydrogenation or dehydrogenation. In addition, we modify our membranes with supported catalysts, e.g. for fuel cell applications.
After impregnation of the ceramic capillary membranes with noble metal seeds, the membranes can be coated inside or outside with a dense metallic layer like palladium by an electroless plating process. Such layers can be further modified by less noble metals like silver, copper or nickel. After tempering alloys can be obtained which are suitable e.g. for hydrogen separation.
Molecular imprinted membranes
For the specific separation of individual components out of a substance mixture we develop new composite membranes consisting of molecular imprinted nanoparticles (so-called Nano-MIPs) with typical particle sizes of between 100 and 300 nm acting as effective selectors. For their synthesis, molecular templates are embedded in the polymer matrix during miniemulsion polymerization. After elution of the templates nanoparticles with highly selective binding sites can be used as a key solution in diverse separation problems arising in the fields of chemical and biological technology.