Anti-adhesive and antimicrobial coatings on ultrafiltration membranes via dopamine-assisted co-deposition of zwitterionic-cationic copolymers

To overcome persistent challenges in membrane biofouling mitigation, we engineered a dual-functional zwitterionic-cationic copolymer architecture and proposed a dopamine-assisted co-deposition strategy for surface modification of polyvinylidene fluoride (PVDF) ultrafiltration membranes, optimizing the surface density of zwitterionic/cationic functional groups. The zwitterionic-cationic copolymers were strategically synthesized via activators regenerated by electron transfer for atom transfer radical polymerization, enabling the synergistic integration of strong hydration capacity and potent bactericidal activity. Key influence factors such as functional unit composition, deposition density, and copolymer chain length on the formation of hydration layers and the hydrophilicity of modified membranes were systematically studied. The PDA/p(DCD)-1-PVDF membrane exhibited substantially enhanced performance versus unmodified counterparts: elevated filtration efficiency (187.4 L·m⁻²·h⁻¹ water flux vs . 175.1 L·m⁻²·h⁻¹ with matching bovine serum albumin rejection), superior antifouling performance (84.78 % corrected total flux recovery ratio vs. 43.12 %), and complete bactericidal efficacy (100% eradication of Escherichia coli and Staphylococcus aureus vs. negligible activity). The dual-defense mechanism relies on zwitterionic groups forming hydration layers to prevent protein adsorption, while cationic groups disrupt bacterial biofilms via electrostatic interactions. This work highlights the potential of zwitterionic-cationic copolymer architectures for enhancing the anti-adhesive and antimicrobial properties of ultrafiltration membranes in a variety of applications.