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 (-CH3) 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 -CH3 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 degrees 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.

Automated summary

pH-responsive materials with switchable wettability were fabricated by grafting long-chain alkanes with carboxyl and methyl groups onto stainless-steel meshes using thiol-ene click chemistry. These pH-responsive meshes exhibited excellent separation efficiency (>97%) in both superhydrophobic and superhydrophilic states, unaffected by the presence of NaCl in the solution.