Surface modification of a PVDF membrane by co-grafting hydroxyl and zwitterionic polymers to enhance wettability and antifouling property

Polyvinylidene fluoride (PVDF) membranes have been widely applied in the separation of various organic matters owing to their excellent properties. However, they possess low wettability and undergo fouling because of the hydrophobic nature of PVDF. In this study, poly (2-hydroxyethyl methacrylate) (PHEMA) and poly (sulfobetaine methacrylate) (PSBMA) were co-introduced to modify the highly hydrophobic PVDF membrane surface via UV photo-irradiation. Facile UV photo-grafting was performed by irradiating the pristine PVDF membrane immersed in a PHEMA/PSBMA mixture solution with UV light for 5 min. The performance of the as-prepared PHEMA/PSBMA-grafted membrane was compared with that of membranes modified with solely PHEMA or PSBMA. The hydroxyl and zwitterionic groups of the grafted membranes enhanced wettability and increased flux. A tightly bound water layer was formed because of the enhanced wettability, significantly suppressing protein adsorption. The initial flux of bovine serum albumin (BSA) solution through the PHEMA/PSBMA-grafted membrane was 2861 LMH, which was 3.1 times higher than that obtained by the pristine PVDF membrane. Furthermore, the flux decline of the modified membrane caused by BSA fouling was 49% lower than that of the pristine PVDF membrane. Finally, the PHEMA/PSBMA-grafted PVDF membrane showed antifouling properties after three BSA filtration cycles.