Grafting zwitterionic brush on the surface of PVDF membrane using physisorbed free radical grafting technique

A facile, effective method was first used to graft zwitterionic monomer sulfobetaine methacrylate (SBMA) onto the surface of PVDF membrane via physisorbed free radical grafting technique. The mechanism of free radical initiating grafting polymerization on PVDF membrane was investigated preliminarily. The key factors affecting the graft density (GD), include monomer concentration, reaction time and the temperature, were investigated in the present study. As the result, the graft density of PSBMA on PVDF membrane was improved with the increasing of monomer concentration and reaction time. Around 70 °C was the optimum temperature for the grafting. Attenuated total reflectance/Fourier transform infrared spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) were conducted to confirm the chemical composition of the membrane surface. The morphology of membranes was characterized by scanning electron microscopy (SEM). After the PSBMA was grafted, the hydrophilicity of membrane surface was improved. The water contact angle decreased from 59° to 17° within 120 s was achieved at the surface of membrane with GD 0.608 mg/cm2. The static protein adsorption and the dynamic fouling-resistance experiment demonstrated that grafting PSBMA on the surface endow PVDF membrane excellent anti-fouling ability.