Reversible dual-stimuli responsive intelligent membrane prepared by RAFT polymerization for on-demand oil-water separation

Abstract

Conventional separation membranes suffer from performance degradation owing to fouling-induced flux decline. To overcome this limitation, this study aims to develop a precision surface engineering strategy for fabricating antifouling membranes with dynamically tunable wettability, enabling on-demand oil-water separation. Initially, polyvinylidene fluoride (PVDF) and poly(2-(dimethylamino) ethyl methacrylate-b-vinyltrimethoxysilane) (P(DMAEMA-b-VTES)) were used as core materials to prepare basement membranes (PVDF/PDV) by non-solvent induced phase separation (NIPS) technology. The VTES segment enabled covalent immobilization of a reversible addition-fragmentation chain-transfer (RAFT) agent through hydrolysis-condensation, facilitating subsequent surface functionalization. Specifically, poly sulfobetaine methacrylate (PSBMA) was grafted to construct superhydrophilic surfaces. The PSBMA-grafted membrane exhibited excellent separation performance, with separation flux reaching 334.6–1155.9 L m⁻² h⁻¹ and efficiency stabilized at 91.5 %–97.3 %. Capitalizing on the “living” nature of RAFT polymerization, the photo-responsive monomer trifluoromethylazobenzene methacrylate (F₃CO-AZO-MA) was further introduced to construct a dynamic wettability control layer, and the PVDF/PDVSM-4 intelligent response membrane was obtained. The membrane can flexibly switch between hydrophilic/hydrophobic and lipophilic/oleophobic properties through the dual regulation of pH and ultraviolet light. This dual-responsive behavior facilitated efficient separation of surfactant-stabilized W/O and O/W emulsions, providing a new idea for on-demand separation and membrane regeneration of complex oil-water systems.