Membrane formation via the combination of self-assembly and the non-solvent induced phase separation (NIPS) process of diblock copolymers is investigated. Several polystyrene-blockpoly(4-vinylpyridine) (PS-b-P4VP) diblock copolymers with different molecular weights and weight percentages of both blocks are tested under different parameters, leading to membrane surfaces with uniform pores of approximately 20-70 nm diameter. The average pore diameter is proved to be adjustable by changing the total molar mass of the block copolymer. The solution composition is an additional parameter controlling the structure formation. The purpose was to explore the limits of the membrane structure formation and find upper and lower limits since the molecular weight and the composition of this diblock cpolymer. Scanning electron microscopy (SEM) is used to image the surface morphology and the homogeneity of the pore sizes. Primary results of water flux and retention are presented.

Double stimuli‐responsive membranes are prepared by modification of pH‐sensitive integral asymmetric polystyrene‐b‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer membranes with temperature‐responsive poly(N‐isopropylacrylamide) (pNIPAM) by a surface linking reaction. PS‐b‐P4VP membranes are first functionalized with a mild mussel‐inspired polydopamine coating and then reacted via Michael addition with an amine‐terminated pNIPAM‐NH2 under slightly basic conditions. The membranes are thoroughly characterized by nuclear magnetic resonance (1H‐NMR), Fourier transform infrared spectroscopy and X‐ray‐induced photoelectron spectroscopy. Additionally dynamic contact angle measurements are performed comparing the sinking rate of water droplets at different temperatures. The pH‐ and thermo‐double sensitivities of the modified membranes are proven by determining the water flux under different temperature and pH conditions.

The formation of an integral asymmetric membrane composed of a cylinder‐forming polystyrene‐block‐poly(2‐vinylpyridine) on a nonwoven by using solvent casting followed by solvent/nonsolvent exchange (phase inversion) is reported for the first time. The influence of parameters such as solvent composition, evaporation time of the solution‐cast block copolymer film before phase inversion, and immersion bath temperature is demonstrated. The optimized membranes are characterized in terms of stimuli‐responsive water flux properties. The morphologies of the membranes as well as of the bulk of the block copolymer are imaged by scanning force microscopy, scanning electron microscopy, and transmission electron microscopy.

The formation of integral asymmetric membranes from ABC triblock terpolymers by non-solvent-induced phase separation is shown. They are compared with the AB diblock copolymer precursors. Triblock terpolymers of polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO) with two compositions are investigated. The third block supports the formation of a membrane in a case, where the corresponding diblock copolymer does not form a good membrane. In addition, the hydrophilicity is increased by the third block and due to the hydroxyl group the possibility of post-functionalization is given. The morphologies are imaged by scanning electron microscopy. The influence of the PEO on the membrane properties is analyzed by water flux, retention, and dynamic contact angle measurements.

The influence of magnesium acetate on the non‐solvent‐induced phase separation (NIPS) process of amphiphilic polystyrene‐block‐poly(4‐vinylpyridine)s to gain integral‐asymmetric membranes is investigated. Highly uniform pores over the large areas of the membrane can be achieved, and the average pore diameter is adjusted by varying the total molar mass of the block copolymers used. These stimuli‐responsive membranes, which are solution cast in the absence or the presence of small amounts of magnesium acetate, are directly compared, showing a remarkable effect on the pore structures and their openness. Minor salt addition is considered to influence the polarity of the solvents used in a positive manner such that the NIPS process can be improved significantly.