Superhydrophobic Surfaces on Phase-separated Nanostructures of Polystyrene/Polymethyl Methacrylate Films Fabricated by the Double-spray Technique

: Rapid large-area printing techniques are required to fabricate superhydrophobic surfaces of polymer films on solid substrates. Here, we report a double-spray technique for fabrication of mixed phase-separated films of polystyrene (PS), poly(methyl methacrylate) (PMMA), and PS-b-PMMA. The surface wettability of the films changes to superhydrophobic by immersing the samples in cyclohexane, which is a good solvent for only PS. The rinsing process forms nanostructures in the remaining PMMA films that have flat surfaces before the rinsing treatment. The highest contact angle is about 150° on the film with a PMMA ratio of 0.2. X-ray photoelectron spectroscopy shows that a small amount of PS remains on the surface of the PMMA films, making the films superhydrophobic. Addition of PS-b-PMMA to the PS/PMMA films forms smaller phase-separated structures than those in the original PS/PMMA films because of an increase in the compatibility between PS and PMMA. The contact angle hysteresis in the films decreases with increasing PS-b-PMMA ratio, indicating an increase in the homogeneity of the phase-separated structures.