Salud Josep, Sebastián Nerea, de la Fuente María R, Diez-Berart S, López David O
Grup de Propietas Físiques dels Materials (GRPFM), Departament de Física, E.T.S.E.I.B. <a href="https://ror.org/03mb6wj31">Universitat Politècnica de Catalunya</a>. Diagonal 647, E- 08028 Barcelona, Spain.
<a href="https://ror.org/05060sz93">Jožef Stefan Institute</a>, Jamova cesta 39, SI-1000 Ljubljana, Slovenia.
Phys Rev E. 2024 Aug;110(2-1):024702. doi: 10.1103/PhysRevE.110.024702.
A comprehensive dynamic analysis of the dielectric relaxation-time data across a broad temperature range for both isotropic and nematic phases has been conducted on the CBO3O.Py liquid crystal dimer, the shorter chain-length compound within the highly nonsymmetric pyrene-based series of liquid crystal dimers (CBOnO.Py, with n ranging from 3 to 11). It was known from another previous study that in the nematic phase, three different relaxation processes contribute to the complex dielectric permittivity depending on the orientation of the alignment axis with respect to the probing electric field direction. The temperature-derivative analysis of the relaxation-time data using different analytic functions reveals that the critical-like description, through the dynamic scaling model, best portrays the relaxation-time data in the nematic phase as the system approaches the glass transition. A single glass transition temperature is obtained which is consistent with thermal stimulated depolarization currents experimental determinations published elsewhere. From temperature-dependent steepness index m(T), the activation-critical model is also considered as a more general analytic function from which the dynamic scaling model is a terminal approximation. Additionally, the critical-like parametrization provides insight into obtaining a universal description of the temperature-dependent steepness index m(T), for all liquid crystal compounds belonging to symmetry-selected glass formers, such as rodlike liquid crystal monomers.
已对CBO₃O.Py液晶二聚体进行了全面的动态分析，该二聚体是高度不对称的芘基液晶二聚体系列（CBOnO.Py，n范围为3至11）中链长较短的化合物，分析涵盖了各向同性相和向列相在很宽温度范围内的介电弛豫时间数据。从另一项先前的研究可知，在向列相中，根据取向轴相对于探测电场方向的取向，三种不同的弛豫过程对复介电常数有贡献。使用不同解析函数对弛豫时间数据进行温度导数分析表明，通过动态标度模型的临界状描述，在系统接近玻璃化转变时能最好地描绘向列相中的弛豫时间数据。获得了单一的玻璃化转变温度，这与其他地方发表的热激发去极化电流实验测定结果一致。从与温度相关的陡度指数m(T)来看，活化临界模型也被视为一种更通用的解析函数，动态标度模型是其最终近似。此外，临界状参数化有助于深入了解如何对属于对称选择的玻璃形成体的所有液晶化合物（如棒状液晶单体）的与温度相关的陡度指数m(T)进行通用描述。
