Amphiphobic polyHIPEs with pH-triggered transition to hydrophilicity-oleophobicity for the controlled removal of water from oil-water mixtures

While emulsion-templated porous polymers (polyHIPEs) with pH-controlled wetting behaviours are advantageous for the removal of oils from oil-water mixtures, they are easily clogged by oils and are not suitable for separating mixtures consisting of a small amount of water and a large amount of oils. Herein, we report the fabrication of amphiphobic polyHIPEs from high internal phase emulsions via simultaneous solution polymerization and interface-induced polymerization. After pH adjustment with an HCl solution, the amphiphobicity of the polyHIPEs was transformed into hydrophilicity-oleophobicity, which enabled water to be selectively absorbed and separated from oil-water mixtures, and the pH-triggered transition achieved the separation in a controlled manner. Moreover, the absorption was realized in a continuous manner under an external pressure provided by a pump. The resulting hydrophilic-oleophobic polyHIPEs also absorbed water from emulsified oil-water mixtures (emulsions). The pH-triggered transition from amphiphobicity to hydrophilicity-oleophobicity and the selective absorption of water from oil-water mixtures in a continuous manner make the polyHIPEs excellent candidates for the controlled removal of water from oil-water mixtures.