Tailoring the dual role of styrene-maleic anhydride copolymer in the fabrication of polysulfone ultrafiltration membranes: Acting as a pore former and amphiphilic surface modifier

To enhance the membrane performances, amphiphilic copolymers are extensively used to modify polymeric membranes by the surface segregation. Notably, they also act as a pore former in the membrane fabrication by the nonsolvent induced phase separation (NIPS). However, it is rarely reported to systematically adjust the pore-forming ability. Herein, a simple method is proposed to simultaneously adjust the surface segregation and pore-forming ability of styrene-maleic anhydride copolymer (SMA (anh)) in the PSF composite membrane formation by its ring opening reaction in the alkaline environment. The surface segregation and pore-forming ability were obviously enhanced accompanying with the miscibility improvement of dope solutions. Subsequently, the membrane microstructure was further optimized by selecting polyethylene glycol (PEG) as the second additive. Significantly, high-molecular-weight PEG was anchored on the membrane surface via strong hydrogen bonding and chain entanglement with sodium styrene-maleic anhydride copolymer (SMA). Compared with the PSF/SMA (anh) membrane, water contact angle (WCA) was obviously reduced due to the cumulative effects of SMA and PEG. Moreover, the resultant membranes displayed the pure water flux of 415.8 L/m2·h·bar, BSA rejection of 98.3 % and flux recovery ratio (FRR) of 95.15 %, which remarkably excelled those reported values for other similar PSF composite membranes.