A copolymer derivative of poly(4-vinylpyridine propylsulfobetaine) for the design of thermostable bioinert poly(vinylidene difluoride) microporous membranes by vapor-induced phase separation

Abstract

Most antifouling membranes lose their bioinert properties after steam sterilization because common antifouling materials are sensitive to hydrolysis. Here, we synthesized a random zwitterionic copolymer containing poly(styrene), poly(ethylene glycol) methyl ether methacrylate and zwitterionic poly(4-vinylpyridine propylsulfobetaine). The resulting copolymer, poly(styrene-r-EGMA-r-4VPPS), was blended with poly(vinylidene difluoride) to form bi-continuous and bioinert PVDF membranes by vapor-induced phase inversion. The copolymer drastically enhanced the hydrophilicity of the membranes, as water could wet the porous substrate entirely (WCA 0 for the zwitterionic membrane vs. about 144° for the virgin membrane). When exposed to Escherichia coli, Stenotrophomonas maltophilia, whole blood or HT1080 cells, fouling on the non-sterilized modified membranes was reduced by 95 %, 98 %, 99 % and 99 %, respectively. After sterilization, the antifouling properties were maintained. Results of cyclic water/Escherichia coli filtrations indicated that the non-sterilized modified membrane showed a flux recovery ratio of 57 %, against 21 % for a commercial membrane. Importantly, these performances were maintained after sterilization. The copolymer is not only efficient at mitigating biofouling in various situations, but also shows stable properties after autoclaving, which is paramount for membranes to be applied in the biomedical field.