Crystal Thickness Dependence of Photoinduced Crystal Bending of 1,2-Bis(2-methyl-5-(4-(1-naphthoyloxymethyl)phenyl)-3-thienyl)perfluorocyclopentene

The photoinduced crystal bending of a photochromic diarylethene derivative, 1,2-bis(2-methyl-5-(4-(1-naphthoyloxyrnethyl)phenyl)-3-thienyl)perfluorocyclopentene (1a), has been particularly investigated. The rodlike crystal of la shows reversible photoinduced bending upon alternating irradiation with ultraviolet (UV) and visible light. The photoinduced crystal bending can be repeated over 80 cycles. The rodlike crystal of la shows different bending behavior depending on the faces irradiated with UV light. This is ascribed to the molecular orientation viewed from the faces. Furthermore, we found that the bending speed depends on the crystal thickness, and the curvature change against the crystal thickness is well-fitted to Timoshenko's bimetal model. These findings provide a new useful strategy to design for the photomechanical actuators.