Design of PVDF/PEGMA-b-PS-b-PEGMA membranes by VIPS for improved biofouling mitigation

Literature on the design of efficient nonfouling membranes by in-situ modification is poor, which can be explained by the difficulty to control membrane formation mechanisms when a third material is added to the casting solution, or by the lack of stability of matrix polymers with surface-modifiers. We present polyvinylidene fluoride membranes formed by vapor-induced phase separation and modified with a tri-block copolymer of poly(styrene) and poly(ethylene glycol) methacrylate moieties (PEGMA(124)-b-PS54-b-PEGMA(124)). After characterizing the copolymer, we move onto membrane formation mechanisms. Membrane formation is well controlled and leads to structure close to bi-continuous. Considering the formulation chosen, PVDF/PEGMA(124)-b-PS54-b-PEGMA(124) solutions are less viscous and more hydrophilic than virgin PVDF solutions. Both effects promote non-solvent transfer, thus decreasing the chances for crystallization. Hydrophilic capability of membranes is increased from about 59 mg/cm(3) to 650 mg/cm(3), leading to a severe drop of non-specific protein adsorption, up to 85-90%, also depending on its nature. Biofouling at the micro-scale by modified Escherichia coli and Streptococcus mutans is almost totally inhibited. Finally, biofouling is importantly reduced in dynamic conditions, as measured from the water flux recovery ratio of 69.4%, after 3 water-BSA filtration cycles, much higher than with a commercial hydrophilic PVDF membrane (47.3%). These membranes hold promise as novel materials for water-treatment or blood filtration. (C) 2016 Elsevier B.V. All rights reserved.