Fabrication of fluorine-free pH-responsive functionalized mesh via thiol-ene click chemistry for oil-water separation

pH-responsive materials with switchable wettability provide a novel strategy for oil-water separation applications. The thiol-ene click chemistry method was used to fabricate pH-responsive stainless-steel meshes (SSM) by grafting long-chain alkanes with carboxyl ( COOH) and methyl ( CH 3 ) groups onto the SSM surface. The pH-responsive SSM showed excellent separation efficiency (>97 %) in both superhydrophobic and superhydrophilic states, which was unaffected by the presence of NaCl in the mixed solution. The pH-responsive SSM demonstrated a fast response within 3 s and a wide pH range after pre-wetting in an alkaline solution (pH spike) due to the presence of long carbon chains containing COOH and CH 3 groups. Moreover, the mesh underwent antifouling, ultraviolet light (UV) resistance, and mechanical resistance tests, showing excellent durability and stability. The water contact angle (WCA) remained higher than 130° after 24 h of UV exposure and six rounds of wear experiments. Furthermore, the oil-water separation efficiency remained above 98.4 % after 20 cycles. The in-depth investigations conducted in this study will provide valuable insights into developing pH-responsive membranes to meet diverse demands, such as water rejection or oil rejection under complex conditions.