Mechanically Responsive Crystals: Analysis of Macroscopic Strain Reveals "Hidden" Processes.,The Journal of Physical Chemistry A

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Mechanically Responsive Crystals: Analysis of Macroscopic Strain Reveals "Hidden" Processes.
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-01-03 , DOI: 10.1021/acs.jpca.9b10365
Israel Tilahun Desta ₁ , Stanislav A Chizhik _{2,

3} , Anatoli A Sidelnikov _{2,

3} , Durga Prasad Karothu ₁ , Elena V Boldyreva _{3,

4} , Panče Naumov ₁

Affiliation

Mechanical response of single crystals to light, temperature, and/or force-an emerging platform for the development of new organic actuating materials for soft robotics-has recently been quantitatively described by a general and robust mathematical model ( Chem. Rev . 2015 , 115 , 12440 - 12490 ). The model can be used to extract accurate activation energies and kinetics of solid-state chemical reactions simply by tracking the time-dependent bending of the crystal. Here we illustrate that deviations of the macroscopic strain in the crystal from that predicted by the model reveal the existence of additional, "hidden" chemical or physical processes, such as sustained structural relaxation between the chemical transformation and the resulting macroscopic deformation of the crystal. This is illustrated with photobendable single crystals of 4-hydroxy-2-(2-pyridinylmethylene)hydrazide, a photochemical switch that undergoes E-to-Z isomerization. The irreversible isomerization in these crystals results in amorphization and plastic deformation that are observed as poor correlation between the transformation extent and the induced strains. The occurrence of these processes was independently confirmed by X-ray diffraction and differential scanning calorimetry. An extended mathematical model is proposed to account for this complex mechanical response.

中文翻译：

机械响应晶体：宏观应变分析揭示了“隐藏”过程。

单晶对光，温度和/或力的机械响应-用于软机器人的新型有机致动材料开发的新兴平台-最近已通过通用且鲁棒的数学模型进行了定量描述（Chem。Rev. 2015，115 ，12440-12490）。通过跟踪晶体随时间变化的弯曲，该模型可用于提取准确的固态化学反应的活化能和动力学。在这里，我们说明了晶体中宏观应变与模型预测的偏离表明存在额外的“隐藏”化学或物理过程，例如化学转化与晶体宏观变形之间的持续结构松弛。用4-羟基-2-（2-吡啶基亚甲基）酰肼的可光弯曲的单晶对此进行了说明，该单晶是经历E到Z异构化的光化学开关。这些晶体中不可逆的异构化导致非晶化和塑性变形，观察到非晶态和塑性变形是相变程度和诱发应变之间的不良相关性。通过X射线衍射和差示扫描量热法独立地证实了这些过程的发生。提出了扩展的数学模型来说明这种复杂的机械响应。这些晶体中不可逆的异构化导致非晶化和塑性变形，观察到非晶态和塑性变形是相变程度和诱发应变之间的不良相关性。通过X射线衍射和差示扫描量热法独立地证实了这些过程的发生。提出了扩展的数学模型来说明这种复杂的机械响应。这些晶体中不可逆的异构化导致非晶化和塑性变形，这被观察为相变程度和诱导应变之间的不良相关性。通过X射线衍射和差示扫描量热法独立地证实了这些过程的发生。提出了扩展的数学模型来说明这种复杂的机械响应。

更新日期：2020-01-04

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