Persistently hydrophilic microporous membranes based on in situ cross-linking

•PVP segments were firmly immobilized in the PVDF membrane due to the well-designed in situ cross-linking reaction.•The obtained membrane exhibited outstanding hydrophilicity and excellent antifouling property.•The newly-developed strategy can be extended to a universal approach to persistently hydrophilic microporous membrane.

An in situ cross-linking route was developed to prepare persistently hydrophilic poly(vinylidene fluoride) (PVDF) membrane, which involved two key reactions, namely, copolymerization of N-vinyl-2-pyrrolidone (NVP) and triethoxyvinylsilane (VTES) and the subsequent hydrolysis condensation between the engineered poly(vinyl pyrrolidone) (PVP) chains. The overall idea of the new technique was to immobilize PVP segments in PVDF membrane via in situ cross-linking reaction and ultimately to obtain membrane with persistent hydrophilicity. Membrane properties were investigated in detail. Scanning Electron Microscopy (SEM) images unveiled that the modified membrane had discretely dotted pores in the surface with finger-like pores in the sublayers. Due to the high content of PVP segments immobilized in membrane surface, the membrane showed much better and more persistent hydrophilicity than the conventional PVDF/PVP blend membranes, as demonstrated by Atom Force Microscopy (AFM) and water contact angle measurement results. Protein adsorption on membrane surface was considerably mitigated, as well as membrane fouling during filtration process. The technique is generic, as it can be used for preparation of other polymeric membranes.