Antifouling PVDF ultrafiltration membranes incorporating PVDF-g-PHEMA additive via atom transfer radical graft polymerizations

The antifouling property of poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membrane incorporating the amphiphilic copolymer additive, poly(vinylidene fluoride)-graft-poly(hydroxyethyl methacrylate) (PVDF-g-PHEMA) synthesized via atom transfer radical polymerization (ATRP), has been investigated. During casting, the PVDF-g-PHEMA additive segregates to form a PHEMA brush layer on all blend membrane surfaces, including internal pores. Polymerization time and monomer content are used as the independent variables to manipulate the amount of grafted PHEMA on PVDF, respectively. The grafting yield of PHEMA is determined by molecular number (Mn) which is increased with the polymerization time and monomer content. The polydispersity index of PVDF-g-PHEMA remains narrow Mw/Mn at around 1.21–1.45 throughout the reaction. The chemical compositions of copolymer and blend membrane are investigated by Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). The morphology of blend membrane is investigated by scanning electron microscopy (SEM). It is found that PHEMA brushes provide higher pure water flux and better anti-protein absorption ability to PVDF membranes. Water permeability of blend membrane using PEG20000 as pore-forming agent is excellent than that using PEG400 due to formation of larger pore sizes on the PVDF membrane surface and some PEG20000 tangling up with copolymers in PVDF matrix. The exceptional anti-fouling performance holds promise for extending UF membrane lifetimes without need for aggressive cleaning procedures.