Synergistic Antifouling and Antibacterial Poly(Lactic Acid) Ultrafiltration Membranes via Plasma‐Initiated Grafting With Zwitterionic and Cationic Copolymer Brushes

Poly(lactic acid) (PLA) is a promising bio‐based polymer for ultrafiltration membranes, yet biofouling remains a critical bottleneck hindering its practical application. Herein, a synergistic “defense and attack” strategy is proposed, in which copolymer brushes of zwitterionic sulfobetaine methacrylate (SBMA) and cationic [2‐(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) are grafted onto the surface of PLA ultrafiltration membranes via plasma‐initiated surface graft polymerization. The modified PLA membranes exhibited significantly enhanced hydrophilicity, with water contact angle (WCA) decreasing from 79.5 ° ± 4.6 ° to 5.9 ° ± 1.3 ° . They also displayed favorable antifouling properties toward bovine serum albumin (BSA) and lysozyme (Lyz), as well as a broad spectrum of antibacterial activity with bacterial reduction rates exceeding 93% against Staphylococcus aureus and Escherichia coli . Dynamic filtration results indicated that the zwitterionic SBMA segments endowed the membrane with reversible fouling behavior and a high flux recovery ratio (FRR) of 92.4% ± 4.9% via the formation of a hydration layer, whereas the cationic METAC moieties offered potent contact‐killing antibacterial ability. Multicycle filtration tests further verified the long‐term stability and fouling reversibility of the SBMA‐rich membranes, validating their potential for continuous operation. This work demonstrates that the synergistic grafting of zwitterionic and cationic copolymers can effectively integrate antifouling and bactericidal functions into a single membrane platform, providing a facile and cost‐effective route for developing green, high‐performance PLA ultrafiltration membranes for advanced water treatment applications.