Polyzwitterions Grafted onto Polyacrylonitrile Membranes by Thiol–Ene Click Chemistry for Oil/Water Separation

Zwitterionic poly(sulfobetaine methacrylate) (PSBMA) was successfully loaded onto a polyacrylonitrile membrane surface by thiol–ene click chemistry. The chemical composition and structure of zwitterionic membrane surfaces were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray (EDX) analysis. An increasing amount of sulfobetaine methacrylate (SBMA) led to a higher density of grafted PSBMA chains, which increased from 0 to 776.7 μg/cm2. As a result, the pores of the membranes were blocked, causing a decrease in the permeation flux of the membranes. The fabricated zwitterionic structure induced superhydrophilicity, underwater superoleophobicity, and oil-fouling resistance to the membrane, as confirmed by contact angle measurements of pure water and oily compounds. The zwitterionic membrane was used for the separation of several oil-in-water emulsions, exhibiting outstanding separation efficiency with more than 99.4% oil removal. The antifouling ability of zwitterionic polyacrylonitrile (PAN) membranes was examined by multicycle filtration. It is found that the reversible and irreversible fouling have been suppressed, which is associated with the recycling of the zwitterionic membrane with a high flux recovery ratio. Generally, surface zwitterionicalization via thiol–ene click chemistry proved to be suitable for the preparation of antifouling polyacrylonitrile membranes for emulsion separation.