Construction of antifouling and alkali resistance of p(VDF-co-AA) membranes realized by carboxyl-anchored in-situ copolymerization

The inherent hydrophobicity of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes exacerbates fouling and limits separation efficiency. To address this, copolymerized poly(vinylidene fluoride- co -acrylic acid) (p(VDF-co-AA)) membranes were fabricated through tert-amyl peroxyneodecanoate (TBPP)-initiated in situ carboxyl group grafting. NMR and XPS verified carboxyl incorporation, while SEM and AFM revealed pore structure refinement (38.44 nm average pore diameter) and increased surface roughness (Ra: increased from 22.7 nm for PVDF membrane to 40.1 nm for p(VDF-co-AA 1.5wt% )). These structural enhancements elevated hydrophilicity, reducing water contact angle by 37.9 % (from 76.65 o  ± 2.16 for PVDF membrane. decreased to 47.64 o  ± 0.66 for p(VDF-co-AA 1.5wt% )) and tripling pure water permeance to 617 L·m −2 ·h −1 ·bar −1 . Molecular dynamics simulations revealed that synergistic hydrogen bonding and carboxyl polar interactions dominated hydrophilicity enhancement. The modified membranes demonstrated outstanding antifouling performance against humic acid (HA), bovine serum albumin (BSA), and sodium alginate (SA), achieving 28.0–38.8 % higher flux retention (J/J 0 ) and 16.7–50.1 % lower irreversible fouling. Notably, the incorporation of carboxyl groups facilitated stable separation performance under extreme alkaline conditions (pH = 14), retaining over 87.6 % of the initial flux and 69.10 % DOC rejection after a 3-day exposure period. This study provides a robust strategy for the development of high-performance UF membranes through molecular-scale hydrophilicity engineering.