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首页> 外文期刊>Advanced Functional Materials >Nematic Phases in 1,2,4-Oxadiazole-Based Bent-Core Liquid Crystals: Is There a Ferroelectric Switching?
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Nematic Phases in 1,2,4-Oxadiazole-Based Bent-Core Liquid Crystals: Is There a Ferroelectric Switching?

机译：1,2,4-恶二唑基弯曲核液晶中的向列相：是否存在铁电开关？

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摘要

Four series of new 1,2,4-oxadiazole derived bent-core liquid crystals incorporating one or two cyclohexane rings are synthesized and investigated by optical polarizing microscopy, differential scanning calorimetry (DSC),X-ray diffraction (XRD), electro-optical, and dielectric investigations. All the compounds exhibit wide ranges of nematic phases composed of tilted smectic (SmC-type) cybotactic clusters with strongly tilted aromatic cores (40-57°) and show a distinct peak in the current curves observed under a triangular wave field. Dielectric spectroscopy of aligned samples corroborates the previously proposed polar structure of the cybotactic clusters and the ferroelectric-like polar switching of these nematic phases. Hence, it is shown that this is a general feature of the nematic phases of structurally different 3,5-diphenyl-1,2,4-oxadiazole derivatives. In these uniaxial nematic phases there is appreciable local biaxiality and polar order in the cybotactic clusters. As a second point it is shown that electric field induced fan-like textures,as often observed for the nematic phases of bent-core liquid crystals, do not indicate the formation of a smectic phase, rather they represent special electro-convection patterns due to hydrodynamic instabilities.
机译：合成并结合了四个新的1,2,4-恶二唑衍生的带有一个或两个环己烷环的弯曲核液晶系列，并通过光学偏振显微镜，差示扫描量热法（DSC），X射线衍射（XRD），电光进行了研究。以及介电调查。所有化合物均表现出宽范围的向列相，该向列相由倾斜的近晶（SmC型）同功簇和强烈倾斜的芳香核（40-57°）组成，并且在三角波场下观察到的电流曲线中显示出明显的峰。对齐样品的介电谱证实了以前提出的等轴晶簇的极性结构以及这些向列相的铁电样极性转换。因此，表明这是结构上不同的3，5-二苯基-1，2，4-恶二唑衍生物的向列相的一般特征。在这些单轴向列相中，在壶形簇中存在明显的局部双轴性和极性顺序。第二点表明，通常在弯曲核液晶的向列相中观察到的电场诱导的扇状纹理并不表示近晶相的形成，而是由于以下原因它们代表特殊的电对流模式：水动力不稳定性。

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  • 来源
    《Advanced Functional Materials》 |2012年第8期|p.1671-1683|共13页
  • 作者

    Govindaswamy Shanker; Mamatha Nagaraj; Antoni Kocot; Jagdish K. Vij; Marko Prehm; Carsten Tschierske;

  • 作者单位

    Institute of Chemistry, Organic Chemistry Martin Luther University Halle-Wittenberg Kurt-Mothes-Str. 2, 06120 Halle, Germany;

    Department of Electronic and Electrical Engineering Trinity College University of Dublin Dublin 2, Ireland;

    Department of Electronic and Electrical Engineering Trinity College University of Dublin Dublin 2, Ireland,Institute of Physics University of Silesia Katowice, Poland;

    Department of Electronic and Electrical Engineering Trinity College University of Dublin Dublin 2, Ireland;

    Institute of Chemistry, Organic Chemistry Martin Luther University Halle-Wittenberg Kurt-Mothes-Str. 2, 06120 Halle, Germany;

    Institute of Chemistry, Organic Chemistry Martin Luther University Halle-Wittenberg Kurt-Mothes-Str. 2, 06120 Halle, Germany;

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