Thermosalience of 1,2,4,5‐Tetrachlorobenzene

Abstract

Crystals undergoing a thermosalient phase transition are capable of small and cooperative rearrangement of their structural units that is converted into rapid and readily observable crystal shape transformation, ballistic events, and/or progression in space. This amplification of dynamics from molecular to macroscopic scale is attractive for fast and efficient conversion of heat into mechanical work in devices such as micromechanical actuators. By using microscopic, thermal and structural analysis here we demonstrate the thermosalient effect in single crystals of 1,2,4,5‐tetrachlorobenzene (TCB), an analogue of the well‐known thermosalient tetrabromo compound. It is shown that TCB crystals are reversibly thermosalient when they transition between two solid phases, labeled forms I and II, however contrary to the tetrabromo compound which is thermosalient above room temperature, the effect occurs below room temperature. Comparison of the structures of the two phases shows that, similar to other thermosalient solids, the two phases of TCB feature identical sheet motif of molecules in their structures, and the transition is governed by subtle changes in the orientation of molecules which are held together by π‐π and weak Cl⋅⋅⋅Cl interactions. This structural perturbation generates strain within the crystal and the sudden release of the accumulated strain results in crystal motion.

Exceptionally high work density of a ferroelectric dynamic organic crystal around room temperature

“…Cooperative phase transitions, and specifically martensitic transitions, are known to be particularly fast transformations 12 , 19 – 21 . Indeed, several recent examples of mechanical effects based on phase transitions in organic crystals, inorganic crystals, hybrid crystals, and a few ionic compounds (both inorganic and organic) have indicated the hidden potential of these materials for fast actuation 22 – 45 . Since the molecular movements are hardly controlled once they are initiated, the realization of practical applications by using dynamic crystals poses challenges with the collective molecular movement and the related lack of control over the mechanical response.…”

Multifunctional Deformable Organic Semiconductor Single Crystals

“…[14,15] Device components that are based on organic (semi)conductors can be implemented in flexible waveguides,f ield-effect transistors,t elecommunication devices,a nd solar cells.T he light weight, determined by their chemical composition, as well as the mechanical robustness and compliance,r ooted in their non-covalent interactions,s tand among the most important aspects of the performance of organic crystals.A long this line of pursuit, their mechanical attributes,which are critically important for durability and robustness of the ensuing devices,a re becoming apopular subject of exploration within the emerging field of crystal adaptronics. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Thep rospects of using dynamic crystals have already been demonstrated with lab-scale applications that include prototypical fuses, [31] transistors, [32] and switches. [33] Of particular interest are the effects of mechanically induced structural transitions in semiconducting single-crystal electrical devices.…”

Room-temperature martensitic actuation profited from one-dimensional hybrid perovskite structure

“…For instance, most application scenarios in smart devices for daily use based on these materials need the transition to occur around room temperature. Other reversible crystals, which actuate above 400 K 39 or lower than 200 K 17,49 have an extreme application scenario. As to 1, the ITP-HTP transition is around 286 K, a temperature point very close to room temperature which is well suited for ambient temperature applications (Fig.…”

“…14 Although the realm of martensitic transformation has expanded into molecular crystals in the past few years, the transformation is not yet fully studied in molecular crystals. [15][16][17] The reason for great interest in molecular martensitic transformation can be attributed to ultrafast and reversible phase transitions in response to thermal/mechanical stimuli and the transition usually bring fascinating properties such as ferroelasticity, thermoelasticity, superelasticity, and shape memory effect. 15,18 These properties are attractive and play an important role in mechanical applications.…”