Antifouling and antibacterial improvement of surface-functionalized poly(vinylidene fluoride) membrane prepared via dihydroxyphenylalanine-initiated atom transfer radical graft polymerizations

Schematic diagram illustrating the process of SI-ATRP from the PVDF membrane. [Display omitted] ► Modification of poly(vinylidene fluoride) membranes via surface-initiated atom transfer radical polymerization. ► Alkyl halide ATRP initiator is immobilized by hydroxyl groups on polyDOPA-coated PVDF membrane surface and pore surface. ► PHEMA graft chains promote remarkably the surface hydrophilicity and antifouling property of PVDF membranes. ► The quaternized PDMAEMA-grafted membranes exhibit excellent antibacterial properties against S. aureus. This work describes the covalently binding of 2-hydroxyethyl methacrylate (HEMA) and 2-(dimethylamino)ethyl methacrylate(DMAEMA) brushes onto the poly(vinylidene fluoride) (PVDF) membrane surfaces via surface-initiated atom transfer radical polymerization (ATRP). Prior to ATRP, PVDF was coated with 3,4-dihydroxyphenylalanine (DOPA). The hydroxyl groups on the polyDOPA-coated PVDF membrane surface and pore surface were used for the immobilization of alkyl halide ATRP initiator. The grafting yield of poly(hydroxyethyl methacrylate) (PHEMA) and poly((dimethylamino)ethyl methacrylate) (PDMAEMA) was determined by weight gain which was linearly increased with the polymerization time. Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscope (AFM) were used to characterize the chemical composition and surface morphology of PVDF membrane and modified membrane, respectively. Water contact angles and water intake measurements indicated that the introduction of PHEMA graft chains promoted remarkably the surface hydrophilicity of PVDF membranes. It was also found that PHEMA graft chains provided higher pure water flux and better anti-protein absorption ability to PVDF membranes. Water flux decreased with increasing polymerization times, while the BSA rejection curves shifted to lower molecular weight cutoff values. The quaternized PVDF-g-PDMAEMA, PVDF-g-PDMAEMA-b-PHEMA membranes exhibited excellent antibacterial properties against Staphylococcus aureus. This study not only introduces a modification approach to obtain a PVDF membrane grafting hydrophilic PHEMA, but also provides the antibacterial properties for PVDF membrane with PDMAEMA.