Flash Shape-Memorization Processing and Inversion of a Polar Direction in a Chiral Organosuperelastic Crystal of 1,3,5-Tricyanobenzene

摘要

Superelasticity—diffusion-less plastic deformation with spontaneous shape recoverability—has been applied to practical uses due to its unique mechanical characteristics, e.g., reversible deformability over elastic limit, and thermally induced shape recovery, the so-called shape-memory effect. For shaping shape-memory alloys showing superelasticity, they are aged under severe conditions unsuitable for organic materials, e.g., heating over several hundred degrees Celsius for several minutes to hours. Here we demonstrate shaping of a chiral organosuperelastic single crystal by quick shape-memorization processing at a temperature between 20 and 170 °C. Different from conventional shape-memory alloys, superelasticity of the crystal shows a small negative temperature dependence. Inversion of a polar direction and helical axis, induced by superelastic deformation in a crystal structure with a polar point group symmetry of 2, is also noteworthy from the viewpoint of polarity-based functions. The unveiled deformability will pave the way for development of organic crystalline materials, e.g., damping materials and structural materials, in soft robots.