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首页> 外文学位 >Ferroelectric and antiferroelectric odd even behavior in a tricarbosilane-terminated liquid crystal homologous series and an electric-field-responsive discotic columnar liquid crystal.
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Ferroelectric and antiferroelectric odd even behavior in a tricarbosilane-terminated liquid crystal homologous series and an electric-field-responsive discotic columnar liquid crystal.

机译：三碳硅烷封端的液晶同系物和电场响应盘状柱状液晶中的铁电和反铁电奇偶行为。

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摘要

Two separate projects on thermotropic liquid crystals are described: an odd-even behavior giving ferroelectric or antiferroelectric phases in a tricarbosilane-terminated liquid crystal homologous series, and an electric-field-responsive discotic columnar liquid-crystal formed from an hexa-peri-hexabenzocoronene/oligothiophene hybrid.;A new class of polyphilic mesogens composed of a tolanphenyl carboxylate core, a chiral alkoxy tail, and a tricarbosilane terminated alkoxy tail were synthesized and shown to self-assemble into nanophase-segregated smectic liquid-crystalline (LC) phases. It was found that the number of carbons in the alkoxy spacer between the tricarbosilane and the core determined the phase observed with perfect fidelity: homologues with odd-carbon spacers exhibit antiferroelectric phases, while those with even-carbon spacers exhibit ferroelectric phases. Even more interestingly, homologues with an odd carbon number show the rare and useful chiral orthoconic antiferroelectric SmCA* phase, in which the optic axis tilt alternates layer to layer between +45° and -45°, making the molecular directors in adjacent layers orthogonal. The even-carbon homologues exhibit the SmC* phase with a 45° tilt angle. These findings demonstrate that the supramolecular self-assembly of polyphilic mesogens may in some cases be controlled by the length of the hydrocarbon spacers.;A novel hexa-peri-hexabenzocoronene (HBC) derivative with six covalently tethered alkyl-trizaole-quadra-3-hexylthiophene units was synthesized via "click" chemistry and shown to self-assemble into a hexagonal columnar liquid-crystal (LC) phase. Compared to other HBC-based LC materials, this mesogen shows unprecedented responses to applied electric fields in cells with thickness of several microns, resulting in uniform homeotropic or parallel alignment depending upon the electrode structure. Furthermore, the columnar orientation, once developed by an applied electric field, can be maintained even after removal of the electric field unless the material is heated above its clearing temperature.
机译：描述了在热致液晶上的两个独立的项目：在三碳硅烷封端的液晶同源序列中给出铁电或反铁电相的奇偶行为，以及由六周六六苯并ron形成的电场响应盘状柱状液晶/低聚噻吩杂化物。合成了由甲苯基苯基羧酸盐核，手性烷氧基尾和三碳硅烷封端的烷氧基尾组成的新型多亲液晶元，并显示出其可自组装成纳米相分离的近晶液晶（LC）相。发现三碳硅烷与核之间的烷氧基间隔基中的碳数目决定了观察到的具有完美保真度的相：具有奇数碳间隔基的同系物显示反铁电相，而具有偶数碳间隔基的同系物显示铁电相。甚至更有趣的是，具有奇数碳原子的同系物显示出罕见且有用的手性正圆锥反铁电SmCA *相，其中光轴倾斜在+ 45°和-45°之间交替变化，使相邻层中的分子指向矢正交。偶碳同系物表现出SmC *相，倾斜角为45°。这些发现表明，在某些情况下，多亲性介晶的超分子自组装可能受到烃间隔基的长度的控制。新型的六-六-六苯并并苯（HBC）衍生物与六个共价连接的烷基-三唑-quadra-3-己基噻吩单元是通过“点击”化学合成的，并显示出自组装成六方柱状液晶（LC）相的能力。与其他基于HBC的LC材料相比，这种液晶元对厚度为几微米的电池中施加的电场表现出空前的响应，这取决于电极结构，导致均匀的垂直排列或平行排列。此外，一旦通过电场施加，即使在去除电场之后，也可以保持柱状取向，除非将材料加热到其清除温度以上。

著录项

  • 作者

    Hu, Nan.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 139 p.
  • 总页数 139
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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