Antibiofouling Polyvinylidene Fluoride Membrane Functionalized\nby Poly(ionic liquid) Brushes via Atom Transfer Radical Polymerization

Biofouling is a multifaceted and\nunavoidable problem in the application\nof membrane separation technology. Here, we functionalized polyvinylidene\nfluoride (PVDF) ultrafiltration membranes with poly­(ionic liquid)\n(PIL) brushes to provide them with antibiofouling properties. The\nPIL brush grafted membranes (PIL-M) were prepared via atom transfer\nradical polymerization (ATRP) using different ionic liquids (ILs)\non the membrane surface. Four functionalized membranes with different\nalkyl chain lengths (C₄-M, C₈-M, C₁₂-M, and C₁₆-M) were prepared to explore the relationship\nbetween surface structure and antibacterial properties. Our results\nshowed that all of the PIL-M had antibacterial capabilities with the\nhighest efficiency of 84.6% for the C₁₂-M. Moreover, the\nantibacterial performance was improved by increasing the ATRP reaction\ntemperature and time. Liposome vesicles were used as the bacterial\ncell membrane model to evaluate the antibacterial membrane damage\nmechanism. IL and PIL brushes could damage cell membranes through\ndisrupting the lipid bilayer with longer alkyl chains associated with\nan enhanced effect. Zeta potential measurements showed that the interference\nof electrostatic interactions with bacteria also played an important\nrole in the bactericidal mechanism. Moreover, filtration experiments\nin a cross-flow system further indicated that PIL-M membranes have\nfavorable antibiofouling performance, with a stable flux increase\n41.7% larger than that of the pristine PVDF membrane. Our results\nsuggest that functionalization of the membrane surface with the PIL\nbrushes can effectively resist bacteria and thereby significantly\nmitigate biofouling on the PVDF membranes.