Abstract
Molecular crystals have medium mechanical properties between inorganic alloys and organic polymers. The material category of molecular crystals has recently shown unique mechanical responses induced by external stimuli such as light, heat, and force. This review explores the superelasticity of molecular crystals, a phenomenon first discovered by Takamizawa et al. in 2014. Molecular crystals can manifest superelasticity by much smaller stresses than typical shape memory alloys, reflecting weaker intermolecular interactions of molecular crystals. A novel photo-responsive occurrence of superelastic deformation was observed in a chiral salicylideneamine crystal, exhibiting photoisomerization and phase transition. This process, involving torsional bending and superelastic deformation within a single crystal, could offer new functionalities in photo-responsive materials. Furthermore, it was found that superelasticity is prevalent across the molecular space by an informatics approach. As data accumulate, materials informatics may unveil the underlying relationship between superelasticity and the structures of molecular crystals, potentially enabling innovative material design.