Rational construction of highly transparent superhydrophobic coatings based on a non-particle, fluorine-free and water-rich system for versatile oil-water separation

Despite the existing effort, fabricating superhydrophobic substrate through an environmental friendly approach remains a great challenge. In the current work, we present a simple approach to fabricate robust superhydrophobic surfaces on different kinds of substrates using phase-separation method. This method uses polydimethylsiloxane (PDMS) as the binder, tetrahydrofuran (THF) as the solvent, and water as nonsolvent. The emulsion prepared under optimum proportion of THF and water was stable and showed no obvious change even after being stored for 6 weeks. The coated substrates exhibit superhydrophobic property with a water contact angle (CA) larger than 155.0 degrees. Moreover, because the solution is rich of water, and the surface modification condition is mild, the PDMS coating enjoys a high degree of transparency. Finally, superhydrophobic cotton and sponge were successfully demonstrated for oil-water and oil-in-water emulsion separation. This facile synthesis method has a potential for a broad range of applications in large-scale fabrication of superhydrophobic surfaces and filtration membranes.