Patterning of photochromic diarylethene crystals by sublimation for morphological controls

We report patterned growth of crystals of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (1a) on the glass substrate with convex guides by sublimation methods. The lower supersaturation of substrate surfaces with higher temperatures can facilitate the vapor-to-melt process rather than the vapor-to-crystal process in the early stage of the sublimation. Micro-droplets of melts of 1a are generated on the sidewalls of the convex guides, then crystallized into the micro-crystals, accompanied by the reconstructions of the crystallographic in-plane orientations. Moreover, the crystalline patterns fringed with the rod crystals are colored in red upon irradiation with ultraviolet light. This well-controllability of crystal morphologies in a simple use of sublimation methods will pave the way for large-sized photomechanical materials with the desired morphologies.