Patterning of Photochromic Diarylethene Crystals by Sublimation for Morphological Controls

A patterned growth of crystals of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (1a) on the glass substrate with convex guides is reported by sublimation methods. The lower supersaturation of substrate surfaces with higher temperatures can facilitate the vapor-to-liquid 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 microcrystals, accompanied by the rearrangements of the crystallographic in-plane orientations. Moreover, the crystalline patterns fringed with the rod crystals are colored 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.