Preparation Of Antifouling PVDF Films By Surface Grafted Hyperbranched Polymers

Poly (vinyl fluoride) (PVDF) membrane has received great attention as a membrane material with regard to its outstanding properties such as high mechanical strength, thermal stability, and chemical resistance, compared to other commercial polymeric materials. However, the lower surface energy and the strong hydrophobic nature of PVDF not only cause membrane fouling by some pollutants in aqueous solution systems, but decrease the water flux, seriously affect the membrane separation performance and service life. Researches show that the enhancement of the surface hydrophilicity of the membrane is helpful to low the inhibition of membrane fouling. Therefore, hydrophilic modification of the PVDF membrane became one of the hot spots in the field of membrane researches. However, the most commonly used polymer brushes are linear molecular chain structure. In this experiment, we chose two kinds of hyperbranched polymers to study its effect on the hydrophilicity and antifouling ability of the membranes.In this study, the antifouling PVDF membranes were prepared by grafting hyperbranched hydroxyl and zwitterionic polymers on the membrane surface via a three-step modification method. The modified membrane was firstly prepared by chemically immobilizing the HPEI on the membrane surface through Michael reaction, then follwed by ring opening reaction of the glycidol and β-propiolactone. The chemical composition of the virgin and modified membranes surface were analyzed by FT-IR and XPS. The surface morphology was characterized by SEM. The surface wettability was measured by dynamic contact angle. The surface charge was characterized by Zeta potential.The results showed that the hydrophilicity of the membrane surface was significantly enhanced when the membrane surface was successfully grafted with glycidol and β-propiolactone. After modification, the water contact angle decreased from 140° to 56°,45°,38° and 58°, indicating super hydrophilicity. We also find that the modified membranes have lower protein adsorption including BSA and LZM. Among them, the PVDFA-g-PG60000 membrane shows the lowest protein adsorption amounts of 45 ug/cm2and 38 ug/cm2. In addition, the modified membranes maintain higher steady water flux recovery ratio and regenerative restoration ability than the virgin PVDF membrane.