Tuning the molecular design of random copolymers for enhancing the biofouling mitigation of membrane materials

Abstract

Abstract Although a lot has been done on the making of antifouling membranes using PEGylated materials, numerous molecular design improvements can still be made on fine-tuning of both composition and chain length. Here, an antifouling copolymer made of styrene and ethylene glycol methacrylate units (PS-co-PEGMA) was used and the results demonstrate that by altering the molar ratio and chain length PS/PEGMA, it can turn the membrane from low-biofouling to almost entirely fouling resistant. At first, a set of 7 copolymers with a molecular weight in a same range but different compositions was prepared, characterized and was used to modify poly(vinylidene fluoride) (PVDF) membranes by vapor-induced phase separation (VIPS) process. Membranes were fully characterized, and antifouling tests carried out with Escherichia coli, Stenotrophomonas maltophilia and fibrinogen all showed that a 30\u202fmol% polystyrene content in the copolymer (PS30P70) led to the best antifouling properties. Increasing or decreasing the styrene amount resulted in increasing the hydrophobicity of the material or decreasing the stability of the modification, respectively, which outcome in both cases was a higher biofouling. Then, 5 copolymers with a fixed composition but different Mws were prepared, and antifouling tests indicated that the longer the chain, the better the antifouling properties. The chain length is essential to the strength of the hydration layer as supported by both mapping FT-IR and DSC measurements.