Miniewicz Andrzej, Orlikowska Hanna, Sobolewska Anna, Bartkiewicz Stanislaw
Advanced Materials Engineering and Modelling Department, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland.
Phys Chem Chem Phys. 2018 Jan 24;20(4):2904-2913. doi: 10.1039/c7cp06820d.
Single-component azobenzene-based phototropic liquid crystals (PtLC) are promising materials that have started to be explored for photonic applications. One of the essential factors determining the applicability of these materials is the rate of the thermally driven cis-trans isomerization. In this paper, the kinetics of the thermal back cis-to-trans reaction in a pure 4-hexyl-4'-methoxyazobenzene (6-AB-O1) compound in its isotropic liquid and nematic phases is studied (the undoped LC). The reaction rate constants, activation energies and thermal activation parameters were determined based on spectroscopic studies. The reaction kinetics is compared to that measured for the compound dissolved in chloroform. The results demonstrate that the thermal back reaction depends on the phase and molecular environment of the cis-isomer. Moreover, the effect of temperature on the absorption spectra of 6-AB-O1 in its isotropic, nematic and crystalline phases is examined. The changes in the compound's absorption spectra in the respective phases have been correlated to the positional order parameter S.
单组分偶氮苯基光致变色液晶（PtLC）是很有前景的材料，已开始被用于光子学应用的探索。决定这些材料适用性的关键因素之一是热驱动顺反异构化的速率。本文研究了纯4-己基-4'-甲氧基偶氮苯（6-AB-O1）化合物在各向同性液体和向列相中的热逆向顺-反反应动力学（未掺杂液晶）。基于光谱研究确定了反应速率常数、活化能和热活化参数。将该反应动力学与溶解在氯仿中的该化合物的测量结果进行了比较。结果表明，热逆向反应取决于顺式异构体的相态和分子环境。此外，还研究了温度对6-AB-O1在各向同性、向列相和晶相中的吸收光谱的影响。该化合物在各相中的吸收光谱变化已与位置有序参数S相关联。
