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

Biofouling is a multifaceted and unavoidable problem in the application of membrane separation technology. Here, we functionalized polyvinylidene fluoride (PVDF) ultrafiltration membranes with poly(ionic liquid) (PIL) brushes to provide them with antibiofouling properties. The PIL brush grafted membranes (PIL-M) were prepared via atom transfer radical polymerization (ATRP) using different ionic liquids (ILs) on the membrane surface. Four functionalized membranes with different alkyl chain lengths (C4-M, C8-M, C12-M, and C16-M) were prepared to explore the relationship between surface structure and antibacterial properties. Our results showed that all of the PIL-M had antibacterial capabilities with the highest efficiency of 84.6% for the C12-M. Moreover, the antibacterial performance was improved by increasing the ATRP reaction temperature and time. Liposome vesicles were used as the bacterial cell membrane model to evaluate the antibacterial membrane damage mechanism. IL and PIL brushes could damage cell membranes through disrupting the lipid bilayer with longer alkyl chains associated with an enhanced effect. Zeta potential measurements showed that the interference of electrostatic interactions with bacteria also played an important role in the bactericidal mechanism. Moreover, filtration experiments in a cross-flow system further indicated that PIL-M membranes have favorable antibiofouling performance, with a stable flux increase 41.7% larger than that of the pristine PVDF membrane. Our results suggest that functionalization of the membrane surface with the PIL brushes can effectively resist bacteria and thereby significantly mitigate biofouling on the PVDF membranes.