Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) and its effect on the surface wettability of PVDF blend membranes

Abstract

Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) was synthesized by radical polymerization technique, and characterized by Fourier transform infrared spectrometry (FTIR), 1H Nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). The resulting copolymer was used to prepare poly(vinylidene fluoride) (PVDF) blend membranes via a phase inversion method. The effects of the copolymer on the polymorphism, surface wettability and zeta potential (ζ) of the blend membranes were investigated by ATR-FTIR, contact angle instrument and zeta potential analyzer. Scanning electron microscopy (SEM and SEM-EDS) was also applied to investigate the morphology and the surface element changes of the fabricated membranes. The results indicated that P(MMA-co-BVIm-Br) copolymer existed on the surface of the membrane which made the blend membrane have a positive surface during the experimental pH range. The copolymer was also in favor of the formation of β crystal phase in PVDF membranes. The contact angle experiment indicated that P(MMA-co-BVIm-Br) copolymer could switch the wettability of the blend membranes from hydrophilic to hydrophobic by exchanging Br− anion with PF6 −. Compared with pure PVDF membranes, the water flux and water recovery flux of the blend membranes were enhanced obviously. The results from the flux recovery ratio (FR) and total fouling ratio (R t) all suggested that the blend membranes had good anti-fouling properties.