Toward Efficient Water/Oil Separation Material: Effect of Copolymer Composition on pH-Responsive Wettability and Separation Performance

Interest in functional soft matter with stimuli-responsive wettability has increasingly intensified in recent years. From the chemical product engineering viewpoint, this study aims to fabricate reversible pH-responsive polymeric surfaces with controllable wettability using [poly(2,2,3,4,4,4-hexafluorobutyl methacrylate)-block-poly(acrylic acid) (PHFBMA-b-PAA)] block copolymers. To attain this aim, three block copolymers with different PAA segment lengths were synthesized for the first time through Cu(0)-mediated reversible-deactivation radical polymerization and hydrolysis reaction. pH-induced controllable wettability was achieved by spin-coating the resulting block copolymers onto silicon wafers. Results showed that the pH-responsive wetting behavior was introduced by incorporating the PAA block, and that the responsiveness of as-fabricated surfaces was greatly influenced by PAA content. All three evolutions of water contact angle with pH shared a similar inflection point at pH 5.25. Furthermore, on the basis of the wetting properties and mechanism understanding, the application of copolymer coated meshes in layered water/oil separation was exploited. Given their superhydrophilicity and underwater superoleophobicity, PHFBMA(70)-b-PAA(148) and PHFBMA(70)-b-PAA(211) coated stainless steel meshes (SSMs) can efficiently separate water from different mixtures of organic solvent and water with high flux. However, considering long-term use, the PHFBMA(70)-b-PAA(148) coated SSM with good stability may be the best copolymer for water/oil separation. Therefore, a coordination of structure, composition, and functionality was necessary to enable practical applications of the functional materials. (C) 2016 American Institute of Chemical Engineers