pH‐Responsive Superwettability Surface: The Study of Oil Dewetting Ability from Air to Water on a Rough Surface and Selective Oil‐Water Separation

Responsive smart surfaces with controllable wettability have a high potential application in self-cleaning and oil-water separation. In this work, a new and simple method is reported to fabricate a pH-responsive superwettability surface. And the self-cleaning performance from air to water after oil contamination in a dry state is studied. Wettability regulation can be achieved by controlling the ratio of carboxyl groups with protonation or deprotonation state in acid or basic solutions. Rough surface with 40% carboxyl content (X-COOH = 0.4) shows the most significant response. The surface is superoleophilic underwater after wetted in acid solution in advance but superoleophobic underwater with basic solution pre-wetted. Oil desorption can be achieved under the superoleophobic state to realize the self-cleaning effect on a rough surface with a complex process. The dynamic self-cleaning process can be achieved by changing the pH value of the solution. This pH-responsive surface also has a good self-cleaning effect for the common water and solid pollutants. Moreover, a smart separation system with the ability to realize selective oil-water separation under two different states is prepared. It is believed that the results reported could broaden the understanding of self-cleaning systems and open a new perspective in controlling wettability.