Design of Mechanically Flexible Photoresponsive Cyanostilbene Molecular Crystals

Abstract

Photoresponsive molecular crystals sparked interest due to potential application prospects. We have achieved dual mechanical responses of cyanostilbene based crystal BN. The crystal exhibited both stress induced mechanical flexibility and light induced photomechanical bending. Two distinct mechanical responses are related to different underlying phenomena and were not interlinked. While elasticity is attributed to criss-cross packing arrangement in isotropic structure, photomechanical bending is ascribed to the formation of heterogeneous phase distribution due to monomer to dimer cycloaddition product formation. The crystal did not demonstrate photoswitching activity. However, it exhibited thermal reversibility pointing to reversible dimer to monomer conversion.