A bio-inert and thermostable zwitterionic copolymer for the surface modification of PVDF membranes

Abstract

This study explores the antifouling properties of membranes dip-coated with a copolymer formed by zwitterionization of poly(styrene-r-4-vinylpyridine), zP(S-r-4VP). 3 copolymers having a different chain length were produced. The NMR analysis showed that the styrene/4-vinylpyridine molar ratio was controlled to 64/36, while XPS tests revealed that the zwitterionization degree ranged between 70% and 80%. Physicochemical evidence was collected proving the efficient coating of zP(S-r-4VP), which in turn provided the membranes with excellent resistance to protein (90% reduction), bacteria (98% reduction) and cells from whole blood (98% reduction) in static condition. Besides, a flux recovery ratio of 50% was obtained after BSA/water cyclic filtration while it was as low as 19% with a commercial hydrophilic membrane in similar conditions. Notably, and unlike with poly(sulfobetaine methacrylate) coatings (PSBMA), steam-sterilization of zP(S-r-4VP)-coated membranes does not alter the antifouling capability of membranes. This novel copolymer not only competes with traditional PSBMA, but outperforms it when sterilization is required, which can be a serious advantage in biomedical applications of membranes.