Characterization of Organoferroelasticity in a TEMPO Crystal

Abstract

For ferroelastic deformation, twinning facilitates the plastic shape change, leaving spontaneous strain. The twinning is common in metal solids in their microstructures and, recently, has been found in organic solids under a single-crystal state. To actualize multiferroicity in organic molecular materials, the crystals consisting of organic free radicals can be candidates, bringing magnetic properties in organoferroelastic solids. Herein, we demonstrated the organoferroelastic deformation of organic radical crystals of (2,2,6,6tetramethylpiperidin-1-yl)oxyl (TEMPO) characterized by force measurements and single-crystal X-ray diffraction analysis.

Structural and Thermal Diffusivity Analysis of an Organoferroelastic Crystal Showing Scissor-Like Two-Directional Deformation Induced by Uniaxial Compression

“…Eventually, a three-point bending test on a universal testing instrument was used to determine the mechanical strength by measuring the elastic modulus of the crystal (Figure S3, SI). ,, The single crystal was subjected to a 14 MPa stress on the face (001/00) in the three-point bending test at RT (Figure S3, Movie S6, SI). The elastic modulus was calculated from the slope of the stress–strain curve of the single crystal (data conversion based on eq S1 and S2, SI).…”

Thermo-mechanical reversibility in a shape memory organic salt

“…A three-point bending test on a universal testing instrument was used to determine the mechanical strength by measuring the elastic modulus of crystal 1 in relation to temperature 23,57,58 (Fig. S7, ESI †).…”

“…3,6 Shape-memory effects are well perceived in alloys and polymers, designated as shape memory alloys 7 (SMAs) and shape memory polymers (SMPs). 8 With the finding of several mechanical deformations such as elastic and plastic bending, [9][10][11] thermosalient, [12][13][14] light-induced mechanical behavior, [15][16][17] mechanosalient, 18 superelastic, [19][20][21] or ferroelastic deformation [22][23][24][25] in organic molecular crystals, crystalline materials are considered desirable candidates for the development of stimuli-responsive intelligent materials along with properties similar to SMAs and SMPs. The shape transition and recovery process in SMAs is executed by a crystalline phase transition called ''thermoelastic transition'' in-between austenitic and martensitic phases in their microstructure with respect to temperature.…”

“…35 Bushuyev et al reported a halogen bondmediated cocrystallization strategy to develop crystalline azobenzene materials exhibiting photo-mechanical and thermochemical properties, thereby enabling the study of in situ isomerization reactions for stimuli-responsive deformation. 36 Furthermore, weak dispersive interactions play a key role in increasing the forward stress 23 in superelastic deformations, which is an essential requirement in sensing and mechanical damping. [37][38][39] These findings provide an opportunity to explore the influence of weak dispersive interactions in dictating and improving mechanical deformation behavior such as ferroelasticity, superelasticity, or the shape memory effect in organic molecular crystals.…”

A role of intermolecular interaction modulating thermal diffusivity in organosuperelastic and organoferroelastic cocrystals

“…Movie S2: shear stress-induced mechanical deformation on the (001) plane of cocrystal 2 by using a pair of tweezers showed that different crystal structures with polar space groups and weak intermolecular interactions such as weak hydrogen bonding, halogen bonding, and van der Waals interactions contribute to superelastic or ferroelastic deformation. [20][21][22] The inuence of weak intermolecular interactions involving halogen groups such as an aromatic C-F group, [23][24][25][26] and halogenhalogen 27,28 and p stacking interactions [29][30][31] on directing the crystal packing in the presence or absence of strong hydrogen bonds has been extensively studied, and can serve as an excellent tool for crystal designing. Li et al suggested that such crystals could be designed by considering the orientational change of molecules caused by twinning in superelastic and ferroelastic deformation.…”