Robustly wettability-switchable polylactic acid nanofibrous membranes bearing CO2-responsive trigger and emulsion breaker for versatile oil–water separation

Wettability-switchable membranes composed of stimuli-responsive polymers and membrane substrates show promising prospects in on-demand oil–water separation, while most of them in practical applications were still limited by their energy-consuming or destructive trigger progresses and substrate non-degradability. Herein, wettability-switchable polylactic acid (PLA) nanofibrous membranes (NFMs) were prepared by grafting CO2-responsive poly(vinyltrimethoxysilane)-co-poly(N,N-dimethylaminoethyl methacrylate) (PVTMS-co-PDMAEMA) copolymers onto PLA NFMs with the assistance of polydopamine (PDA) coating, and named as PLA@PDA/DMA-V NFMs whose successful preparation was confirmed by surface morphology and chemical composition analyses. The membrane wettability could be controllably switched by regulating the CO2-responsiveness of PDMAEMA segments, endowing PLA@PDA/DMA-V NFMs with "oil-removing" or "water-removing" abilities. Consequently, PLA@PDA/DMA-V NFMs presented outstanding on-demand separation performances for differently immiscible oil–water mixtures with exceptional flux (up to 12,865 L m−2 h−1), separation efficiency (up to 99.99 %) and cyclic reusability. Moreover, PDMAEMA segments acted as emulsion breakers could facilitate demulsification, thus PLA@PDA/DMA-V NFMs also exhibited excellent separation performances against various water-in-oil and oil-in-water emulsions with high flux (up to 5015 L m−2 h−1), separation efficiency (up to 99.83 %) and satisfactory recyclability. Additionally, benefiting from the in-situ switchable wettability, PLA@PDA/DMA-V NFMs achieved the continuous separation of heavy oil–water-light oil ternary mixtures with ultrahigh flux (>10000 L m−2 h−1) and separation efficiency (99.99 %). Overall, this work opens up a promising approach to develop environment-friendly, wettability-switchable membranes triggered by energy-saving and clean stimuli for versatile oil–water separation.