(709a) Fouling-Resistant Block Copolymer Membranes By Simultaneous Selective Swelling and Zwitterization

We report on a new strategy to produce zwitterization-enabled fouling-resistant membranes, in which zwitterization and formation of membrane pores take place simultaneously. This strategy is enabled by selective swelling of block copolymers (BCPs) in the presence of zwitterization agents. We synthesized the BCPs of poly(2-dimethylaminoethyl methacrylate) and polystyrene (PDMAEMA-b-PS) via reversible addition fragmentation chain transfer (RAFT) polymerization. The BCP was coated onto macroporous supports to produce composite structures, which were then soaked in hot ethanol to induce the selective swelling of the PDMAEMA microdomains. 1, 3-propane sultone (1, 3-PS) was dosed into ethanol to simultaneously zwitterizate the tertiary amine groups in the PDMAEMA chains. During the swelling process, the PDMAEMA chains spontaneously migrated onto the interfaces (including membrane surface and pore walls), and the surface-enriched PDMAEMA chains were transformed into zwitterionic poly(sulfobetaine methacrylate) (PSBMA) by the quaternization with 1,3-PS. Upon evaporation of ethanol after removing the membranes from the swelling bath, well-defined nanoporous structures in the BCP layers were formed with PSBMA chains uniformly along the pore walls. Nanoporous BCP films served as the separation layers of thus-obtained composite membranes. On account of the zwitterionic polymers, the composite membranes exhibit excellent perm-selectivity and fouling-resistance. Moreover, their separation properties can be readily regulated by swelling conditions as well as concentrations of 1, 3-PS.