Micro/nanotextured polymer coatings fabricated by UV curing-induced phase separation: creation of superhydrophobic surfaces

Inspired by naturally occurring superhydrophobic surfaces, a number of approaches have been attempted to create specific surfaces having both micro- and nanoscale textures. To bring the artificial superhydrophobic surfaces closer to practical applications, a widely usable and simpler method that is systematically derived is required. Here, we describe a unique UV light-triggered micro/nanofabrication system for creating superhydrophobic surfaces, where the basic idea underlying this method comes from polymerization-induced phase separation (PIPS) phenomena. The operation consists of a three-step sequence and can be quickly performed within several minutes under an open-air condition: (1) coating of a precursor mixture for PIPS on a substrate, (2) UV curing to induce phase separation between the growing polymers and solvents, and (3) ethanol flushing to remove solvents to leave a specific texture at the surface. By selecting appropriate components of the PIPS mixture (cross-linkable monomers, solvents, and soluble polymer additives), phase separation rapidly and effectively occurred even in the film UV-polymerization format through the increasing thermodynamic instability; thereby specialized surfaces having micro- and nanoscale textures could be logically constructed. On the basis of the systematic investigation, this method was thus proved to be versatile and applicable for rational design of creating both transparent superhydrophobic films and water repellent fabric textiles.