Multifunctional pH-Switched Superwetting Copolymer Nanotextile: Surface Engineered toward on-Demand Light Oil–Water Separation on Superhydrophilic–Underwater Low-Adhesive Superoleophobic Nonwoven Mesh

The high performance of an oil–water separator relies largely on unique design of the architecture with a hierarchical and porous morphology as well as smart wetting responsiveness of active materials. A well-structured NaOH-treated antioil nonwoven mesh with in-situ and ex-situ pH-switched wetting was successfully prepared by controlled electrospinning of SAN copolymer followed by thermal treating in NaOH aqueous solution. The as-obtained robust and flexible pH-switched antioil mesh with highly accessible pH-responsive groups and a 3D open porous network geometry not only will achieve durable superhydrophilicity/superoleophobicity in air but also a superior underwater low-adhesive superoleophobicity could be obtained, leading the surface to be successfully used for long-term usage immiscible/emulsified light oil–water separation using only gravity-driven force with excellent antioil fouling during multiple cycles. Simultaneously, the water-soluble pollutant could be effectively captured by the antioil mesh and simply released in ethanol media. The “extended coil conformation” and “intermolecular hydrogen bonding” are proposed to explain the antioil wetting behavior. Most importantly, smart reversible pH switching from antioil to antiwater wetting could be simply and quickly obtained only by immersing the NaOH-treated mesh in acidic-aqueous solution to obtain an acid-treated antiwater mesh acting in “oil removing”, which is repeatedly cycled without causing any damage to the mesh and loss of pH responsiveness. It is believed that such highly cost-effective and commercially scaled up smart material will be a promising candidate for use in removal of oil-polluted waters in the future.