Fine Switching between Underwater Superoleophilicity and Underwater Superoleophobicity while Maintaining Superhydrophobicity.

Switching between superhydrophobicity/underwater superoleophilicity and superhydrophilicity/underwater superoleophobicity has been widely designed. Recently, superwettability is subdivided into multiple extreme wetting states for oil, water, and air as wetting and medium phases. However, fine switching among the multiple superwettability is rare. Here, a pH-responsive case is presented to demonstrate the fine switching between underwater superoleophilicity and underwater superoleophobicity while maintaining superhydrophobicity. The surface chemistry of silver-roughened copper coatings is elaborately manipulated by water-repellent perfluoroalkyl and alkyl chains and the smart terminal carboxyl group. By adjusting the pH value of water, the completely opposite extreme wetting states for oil in water are precisely controlled. Simultaneously, the extreme repellence for water in the air can be kept owing to the fairly low surface energy of the perfluoroalkyl chain. This discovery accelerates the subdivision of superwettability and the achievement of unusual superwetting switching.