Morphology, wettability and photomicropatterning of superhydrophobic surface with high adhesive force by crystal growth of a photochromic diarylethene

Abstract

A photochromic diarylethene, 1,2-bis(2-methyl-6-nitro-1-benzothiophen-3-yl)perfluorocyclopentene (1a), can undergo crystallization from the amorphous film in poly(methyl methacrylate) (PMMA) at 130 °C. The contact angle with water on the film changed from 82 to 132° upon crystallization. Moreover, by heating at 180 °C, the contact angle increased to 154°, showing a superhydrophobic surface (water contact angle >150°). The change in the contact angle can be ascribed to the surface roughness change by the crystal growth. The superhydrophobic surface also showed high-water adhesive properties. Patterning of the superhydrophobic and hydrophobic surfaces was performed using a photomask by photoirradiation leading to a resolution of about 10 μm. The contact angle on the photoirradiated area was reduced to 138° along with lowering of the surface roughness because of poorer crystal growth of the photoirradiated crystals. Such a superhydrophobic surface with high adhesive force is useful for water capturing devices.