Fine Switching between Underwater Superoleophilicity\nand Underwater Superoleophobicity while Maintaining Superhydrophobicity

Abstract

Switching\nbetween superhydrophobicity/underwater superoleophilicity\nand superhydrophilicity/underwater superoleophobicity has been widely\ndesigned. Recently, superwettability is subdivided into multiple extreme\nwetting states for oil, water, and air as wetting and medium phases.\nHowever, fine switching among the multiple superwettability is rare.\nHere, a pH-responsive case is presented to demonstrate the fine switching\nbetween underwater superoleophilicity and underwater superoleophobicity\nwhile maintaining superhydrophobicity. The surface chemistry of silver-roughened\ncopper coatings is elaborately manipulated by water-repellent perfluoroalkyl\nand alkyl chains and the smart terminal carboxyl group. By adjusting\nthe pH value of water, the completely opposite extreme wetting states\nfor oil in water are precisely controlled. Simultaneously, the extreme\nrepellence for water in the air can be kept owing to the fairly low\nsurface energy of the perfluoroalkyl chain. This discovery accelerates\nthe subdivision of superwettability and the achievement of unusual\nsuperwetting switching.