Shape Rememorization of an Organosuperelastic Crystal through Superelasticity–Ferroelasticity Interconversion

Abstract

As altering permanent shapes without loss of material function is of practical importance for material molding, especially for elastic materials,s hape-rememorization ability would enhance the utility of elastic crystalline materials.Since diffusionless plastic deformability can preserve the crystallinity of materials,t he interconversion of diffusionless mechanical deformability between superelasticity and ferroelasticity could enable shape rememorization of superelastic single crystals.T his study demonstrates the shape rememorization of an organosuperelastic single crystal of 1,4-dicyanobenzene through time-reversible interconversion of superelasticity-ferroelasticity relaxation by holding the mechanically twinned crystal without heating. The shaperememorization ability of the organosuperelastic crystal indicates the compatibility of superelasticity (antiferroelasticity) and ferroelasticity as well as the intrinsic workability of organic crystalline materials capable of recovering their crystal functions under mild conditions. Practical applications of solid materials demand not only appropriate functions but also appropriate shapes.S ome polycrystalline and amorphous materials,s uch as alloys and polymers,are available in various shapes through molding in ad iffusion manner by thermal processes,i nw hich thermal stability is essential. On the other hand, reshaping singlecrystalline materials,i nw hich at hree-dimensional order is kept, is achieved by ac ombination of cutting,f iling, [1] and etching [2,3] according to their physical and chemical characteristics and intended use.R ecently,t he mechanical deformability of organic crystals has attracted great attention. Among their properties,s uperelasticity (SE) [18,[28][29][30][31] and ferroelasticity (FE) [19][20][21][22][23][24][25][26] give crystallographically well-regulated deformability while retaining single crystallinity. SE and FE have been developed in the fields of the materials science of metal alloys and the physics of ferroics, [32] respectively.M echanical deformations through both SE and FE are realized by diffusionless plastic deformability, whereby SE spontaneously recovers from strain and FE leaves permanent strain. In so-called shape-memory alloys (SMAs), [33][34][35] the shape is recovered because of the thermal generation of SE by as olid-state phase transition based on Gibbs free energy gaps,t hat is,m artensitic SE (mSE). Therefore,twinning deformation irrelevant to phase changes basically leads to twinning FE (tFE). Although tFE was claimed in an organic crystal of squaric acid in 1979, [19] tFE has now been identified in an increasing number of organic crystals and become commonplace in organic crystals composed of structurally flexible molecules. [19][20][21][22][23][24][25][26] Furthermore, multiple tFE effects with versatile deformability have been found in a1 ,4-diethoxybenzene crystal. [26] Tw inning deformability is apotential effective reshaping procedure for organic single crystals.Some organic crystals exhibit SE, so-called...

A Multidirectional Superelastic Organic Crystal by Versatile Ferroelastical Manipulation

“…Mechanical twinning has been well‐studied in inorganic materials but less attention has been paid to brittle and tiny organic molecular crystals even though their anisotropy and single crystallinity in each domain enables fruitful information about twinning at the molecular level to be obtained by X‐ray crystallographic studies. Recently, mechanical twinning in organic crystals showing superelasticity (SE α/αs/α )—spontaneous shape recovery—or ferroelasticity (FE α/αf/α )—spontaneous strain—have been found to be more common than previously thought. Versatile deformability without losing crystallinity was firstly observed in a ferroelastic organic single crystal with multiple mechanical twinning based on a molecular zone axis which resulted in various molecular orientations separated in domains.…”

Super‐ and Ferroelastic Organic Semiconductors for Ultraflexible Single‐Crystal Electronics

“…This fascinating deformation mechanism, known as a martensitic transformation, underlies (thermo)mechanically induced phase transitions and lattice reorientations of shape memory alloys . This intriguing feature has also been discovered very recently in molecular crystals . For instance, Takamizawa and co‐workers demonstrated the superelasticity of terephthalamide based on a reversible transition between two mechanically interconvertible polymorphs .…”

A Multidirectional Superelastic Organic Crystal by Versatile Ferroelastical Manipulation

“…Mechanical twinning has been wellstudied in inorganic materials [14] but less attention has been paid to brittle and tiny organic molecular crystals [15][16][17][18][19] even though their anisotropy and single crystallinity in each domain enables fruitful information about twinning at the molecular level to be obtained by X-ray crystallographic studies. Recently, mechanical twinning in organic crystals showing superelasticity (SE a/as/a )-spontaneous shape recovery [13,[20][21][22][23] -or ferroelasticity (FE a/af/a )-spontaneous strain [24][25][26][27][28][29][30] -have been found to be more common than previously thought. Versatile deformability without losing crystallinity was firstly observed in a ferroelastic organic single crystal with multiple mechanical twinning based on a molecular zone axis [30] which resulted in various molecular orientations separated in domains.…”