Prof. Dr. Axel Müller

Asymmetric membranes are prepared via the non-solvent-induced phase separation (NIPS) process from a polystyrene-block-poly(N,N-dimethylaminoethyl methacrylate) (PS-b-PDMAEMA) block copolymer. The polymer is prepared via sequential living anionic polymerization. Membrane surface and volume structures are characterized by scanning electron microscopy. Due to their asymmetric character, resulting in a thin separation layer with pores below 100 nm on top and a macroporous volume structure, the membranes are self-supporting. Furthermore, they exhibit a defect-free surface over several 100 µm². Polystyrene serves as the membrane matrix, whereas the pH- and temperature-sensitive minority block, PDMAEMA, renders the material double stimuli-responsive. Therefore, in terms of water flux, the membranes are able to react on two independently applicable stimuli, pH and temperature. Compared to the conditions where the lowest water flux is obtained, low temperature and pH, activation of both triggers results in a seven-fold permeability increase. The pore size distribution and the separation properties of the obtained membranes were tested through the pH-dependent filtration of silica particles with sizes of 12-100 nm.