Molecular design of antifouling ultrafiltration membranes via copolymerization of bactericidal and hydrophilic polymers

Membrane fouling is still a significant obstacle to applying polyvinylidene fluoride (PVDF) ultrafiltration membranes. We developed bactericidal and hydrophilic comb copolymers to address this issue by introducing quaternary ammonium compounds (QAC) and sulfobetaine methacrylate (SBMA) onto PVDF powder. Utilizing atom transfer radical polymerization, we synthesized a series of polymer brushes by adjusting the QAC and SBMA functional monomers ratio. These polymer brushes were then employed to fabricate modified membranes featuring diverse alkyl chain lengths and hydrophilic layers. All modified membranes exhibited antibacterial and anti-adhesion properties. Increasing the SBMA monomer ratio resulted in reduced membrane pore size, a smoother membrane surface, and enhanced hydrophilicity. This balanced approach synergistically integrates "defensive" and "offensive" strategies, adjusting polymer proportions to confer dual functionality of hydrophilicity and bactericidal action in ultrafiltration membranes. Notably, the functionalized PVDF powder with copolymer chains exhibited a high inhibition efficiency of 100% against E. coli and 52.0% against E. faecalis, and the optimized membranes have an impressive performance of effectively preventing bacteria adhesion and inactivating attached bacteria. Dynamic filtration experiments further revealed the superior anti-biofouling capabilities of the modified membrane. Furthermore, the membrane containing 50% SBMA and 50% QAC exhibited a 69.5% improvement in anti-organic performance compared to those with only QAC. Our study presents a straightforward and efficient approach for designing antifouling PVDF membranes, showing great promise for wastewater treatment applications.