Photomechanical Functions of Diarylethene Molecular Crystals

Abstract

  Single crystals of diarylethene molecular photoswitches not only show reversible color changes but also undergo shape deformation upon photoirradiation. The surface morphology as well as the bulk shape of the single crystals reversibly changes upon photoisomerization reactions of the component diarylethene molecules in the crystals. This phenomenon is ascribed to anisotropic deformation of the crystal lattice induced by geometrical structure changes of the diarylethene molecules upon photoisomerization. The photodeformable crystals perform macroscopic mechanical works, such as launching a silica micro-particle, lifting up a metal ball, and rotating a gearwheel. Controlling the crystal growth and hybridizing the single crystals with polymer materials are effective for fabricating advanced photomechanical materials. In addition, external mechanical stimuli change the arrangement and photoresponses of component molecules in crystals, leading to the emergence of dynamic mechanoresponsive photoluminescence. These observations suggest that constructing crystalline assemblies of photochromic molecules is a promising approach to create responsive materials that show macroscopic photomechanical performance.