A novel method to immobilize zwitterionic copolymers onto PVDF hollow fiber membrane surface to obtain antifouling membranes

Zwitterionic materials are considered to be a promising new-generation non- or low-fouling materials. However, stable, and straightforward introduction of zwitterions into membranes for commercial production remains as a big challenge yet. Herein for the first time we propose a simple approach to immobilize zwitterionic copolymers on poly(vinylidene fluoride) (PVDF) hollow fiber membrane (HFM) surfaces with considerably high stability via surface entrapment and subsequent simple reactions. First, a commercial amphiphilic copolymer, viz. styrene-malefic anhydride (PSMA), was entrapped on the outer surface of PVDF membranes using co-extrusion by a triple orifice spinneret. PSMA exhibited excellent stability on the PVDF membrane, and its reactive anhydride (MA) group was stabilized on the outer membrane surface. Next, the commercially available zwitterionic copolymer poly(2-methacryloyloxyethyl phosphorylcholine-co-2-aminoethyl methacrylate hydrochloride) (P (MPC-AEMA)) was immobilized on the PVDF/PSMA membrane surface by a simple reaction between the MA groups of PSMA and the amine groups of P(MPC-AEMA). The P(MPC-AEMA) reacted membrane exhibited noticeable bovine serum albumin (BSA) antifouling and antibacterial properties during both static adsorption and dynamic filtration. The flux recovery ratio (FRR) of the membrane exceeded 80% after seven cycles of BSA filtration. The modified membrane showed an even higher FRR (similar to 95%) during bacterial filtration, and such excellent performance was attributed to its super hydrophilicity. Our novel, advanced and straightforward modification method lights on a spotlight for a new pathway to make immobilization of zwitterions on polymeric membrane without needing complicated reactions or procedures.