Direct in-situ modification of PVDF membranes with a zwitterionic copolymer to form bi-continuous and fouling resistant membranes

This study addresses the challenge of blending poly(vinylidene fluoride) (PVDF) and a zwitterionic copolymer of styrene units, sulfobetaine methacrylate units and ethylene glycol methacrylate units (PS-r-PEGMA-r-PSBMA) to form fouling-resistant membranes in one step. Membranes with a lacy structure were obtained. Fouling tests highlighted the very good efficiency of the copolymer, but the influence of the zwitterionic groups was only seen in harsher conditions: the addition of PSBMA in the copolymer improved the fouling resistance after incubation of the membranes with fibrinogen from platelet-poor-plasma, bacteria or whole blood. The zwitterionic membrane outperformed the commercial hydrophilic PVDF membrane in permeability tests after incubation with a platelet-poor-plasma solution with a FRR of 91% while it was 66% with the commercial membrane. Overall, these results show that using a solubility enhancing block (here PEGMA) can permit to take full advantage of the excellent antifouling properties of zwitterionic materials and readily prepare fouling-resistant membranes in one step.