Reversible dual stimuli-responsive polymer coatings with antimicrobial properties for oil–water separation

Efficient separation of increasingly complex oil–water mixtures demands advanced materials capable of adaptive, on-demand performance under diverse environmental conditions. Conventional single-function separation materials often fail to meet these challenges, particularly in achieving controllable separation in dynamic or contaminated environments. This highlights the pressing need for intelligent materials to help mitigate global water pollution and oil scarcity. In this study, a series of reversible dual-stimuli-responsive polymers were synthesised via a straightforward one-step reversible addition-fragmentation chain transfer (RAFT) polymerisation method. Incorporating azobenzene-based photoswitches and pH-responsive units, these polymers exhibit significant and reversible responsiveness to both UV irradiation and pH variation. When coated onto stainless steel wire meshes, the resulting reusable membranes demonstrated excellent performance in separating oil–water mixtures. Under alkaline conditions or upon irradiation with 445 nm light, the membranes exhibited a maximum water contact angle of approximately 140°. In contrast, under acidic conditions or 365 nm UV exposure, the membranes switched to a superhydrophilic state with a contact angle of around 6°, resulting in a maximum contact angle variation of 134°. Additionally, antibacterial assays revealed a maximum inhibition rate of 75.1%, confirming the coatings’ potential effectiveness in biological environments. This work demonstrates a bright strategy for designing multifunctional and controllable oil–water separation coatings, with potential applications in complex, real-world settings requiring both separation efficiency and antibacterial properties.