Electrospun fiber membranes from blends of poly(vinylidene fluoride) with fouling-resistant zwitterionic copolymers

Nonwoven super-hydrophobic fiber membranes have potential applications in oil-water separation and membrane distillation, but fouling negatively impacts both applications. Membranes were prepared from blends comprising poly(vinylidene fluoride) (PVDF) and random zwitterionic copolymers of poly(methyl methacrylate) (PMMA) with sulfobetaine methacrylate (SBMA) or with sulfobetaine-2-vinylpyridine (SB2VP). PVDF imparts mechanical strength to the membrane, while the copolymers enhance fouling resistance. Blend composition was varied by controlling the PVDF-to-copolymer ratio. Nonwoven fiber membranes were obtained by electrospinning solutions of PVDF and the copolymers in a mixed solvent of N,N-dimethylacetamide and acetone. The PVDF crystal phases and crystallinities of the blends were studied using wide-angle X-ray diffraction and differential scanning calorimetry (DSC). PVDF crystallized preferentially into its polar beta-phase, though its degree of crystallinity was reduced with increased addition of the random copolymers. Thermogravimetry (TG) showed that the degradation temperatures varied systematically with blend composition. PVDF blends with either copolymer showed significant increase of fouling resistance. Membranes prepared from blends containing 10% P(MMA-ran-SB2VP) had the highest fouling resistance, with a fivefold decrease in protein adsorption on the surface, compared to homopolymer PVDF. They also exhibited higher pure water flux, and better oil removal in oil-water separation experiments. (c) 2018 Society of Chemical Industry