Antifouling Ultrafiltration Membranes with Enhanced Stability and Hydrophilicity by Self-assembly and Cross-linking of Block Copolymer Additives

Membranes prepared by classical nonsolvent-induced phase separation (NIPS) are often criticized for disadvantages such as a thick, dense skin layer; low porosity; and a wide pore size distribution. The use of polymeric additives can enhance the membrane's hydrophilicity, permeability, and antifouling performance. However, the leaching of traditional hydrophilic polymeric additives could limit the long-term operation performance of the membranes. Herein, amphiphilic block copolymer Poly(PEG-b-EAMO) with pendant photopolymerizable functional groups was prepared by controlled radical polymerization and used as additives for membrane fabrication. PVDF membranes were prepared through either simple blending modification or blending combined with in situ cross-linking by cationic photopolymerization, respectively. The hydrophilicity of the modified membranes was enhanced, and the adsorption capacities of bovine serum albumin (BSA) and humic acid (HA) were significantly reduced. The water contact angle of M0 was 86.1°. At the same time, M5 had the lowest contact angle of 63.3°. M5 also exhibited the lowest adsorption (16.2 and 5.4 μg/cm2 for BSA and HA, respectively), which were significantly lower than those of M0 (45.1 and 22.0 μg/cm2, respectively). The optimum membrane M5 with superior hydrophilic and antifouling properties had the highest retention for BSA and HA, as well as flux recovery rates (FRR). During the first water-BSA-water cycle test, M5 exhibited the highest FRR (80.6%), while M0 had a much lower FRR of only 46.5%. A similar trend was observed in the water-HA-water cycle test, where M5 achieved the highest FRR (91.0%) in the first cycle. In addition, M5 also showed excellent stability and still maintained excellent hydrophilicity and permeability after 48 h of ethanol immersion.