A simplified method for preparation of hydrophilic PVDF membranes from an amphiphilic graft copolymer

Abstract

An attempt to reduce the number of steps and hence the overall costs involved in the preparation of hydrophilic flat sheet poly(vinylidene fluoride) (PVDF) membranes was made by adding PVDF polymer powders directly to an amphiphilic copolymer mixture containing PVDF grafted with poly(ethylene glycol) methyl ether methacrylate (PEGMA) (PVDF-g-PEGMA), solvent and unreacted PEGMA from the atom transfer radical polymerisation (ATRP) method. The membrane was characterised by Fourier transform infra-red attenuated reflection spectroscopy (FTIR-ATR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM), pure water flux, contact angle measurement and protein filtration experiments. The presence of ester and ether groups attributable to the PEGMA in the resultant membrane was observed from FTIR-ATR spectra. From SEM and FESEM observations, an asymmetric membrane was formed with a thin skin layer accompanied by short finger-like and macrovoid structures, but the membrane morphology changed when the copolymer content was increased. AFM reveals that the roughness of the membranes becomes greater with higher amount of PVDF-g-PEGMA. The pure water permeation flux of the prepared membrane increased significantly to 116 L/m 2 h compared to pure PVDF membranes, while contact angle measurements show a moderate value of between 57° and 67°. The percentage of fouling recovered using water cleaning after protein filtration was found to be 100% for all membranes prepared from this method. The results suggested that hydrophilic and low-fouling PVDF membranes were formed from the newly developed method. Since membrane hydrophilicity has a pronounced effect on the fouling properties, hydrophilic PVDF membranes developed from this process are anticipated to be suitable not only for bio-separation, but also for wastewater treatment.