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Photomodulation of the spontaneous polarization of ferroelectric liquid crystals using chiral thioindigo dopants.

机译：使用手性硫靛蓝掺杂剂对铁电液晶的自发极化进行光调制。

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摘要

Ferroelectric liquid crystals (FLC) are chiral smectic C (S{dollar}sb{lcub}rm C{rcub}sp*){dollar} phases that exhibit a spontaneous polarization (Ps). This permanent dipole moment is a macroscopic manifestation of molecular chirality. Between crossed polarizers, a FLC becomes a light valve by switching the orientation of Ps using an applied electric field. Due to the bistability exhibited by FLC light valves, any digital information written in such devices is kept for an indefinite period of time in the absence of the electrical field. The switching of the orientation of Ps can also be achieved optically if the FLC media is photoresponsive. Thus, an erasable optical memory device can be developed.; Optically addressed FLC light valves have been developed based on the photomodulation of Ps via the so-called photomechanical effect, which works on the principle of destabilizing the FLC phase using azobenzene dopants that absorb in the UV region of the spectrum. In the work described here in, we propose the following approach: to photomodulate the spontaneous polarization of a ferroelectric liquid crystal by modulating the transverse dipole moment of a chiral thioindigo dopant. This dopant undergoes a reversible cis-trans isomerization when irradiated in the visible range of the spectrum, and maintains a rod-like shape in both isomeric forms.; In the first part of the project, we synthesized a series of 6,6-dialkoxythioindigo dopants and tested their solubility properties in a variety of S{dollar}sb{lcub}rm C{rcub}{dollar} and nematic liquid crystals. Based on these results, we synthesized the first chiral thioindigo dopant (R,R)-1a with improved solubility in S{dollar}sb{lcub}rm C{rcub}{dollar} hosts. This compound was doped in a phenyl benzoate S{dollar}sb{lcub}rm C{rcub}sp*{dollar} host to induce a ferroelectric S{dollar}sb{lcub}rm C{rcub}sp*{dollar} phase and irradiated to cause trans-cis photoisomerization, which resulted in negligible photomodulation of Ps due to the absence of steric coupling between the thioindigo core and the chiral side-chains.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI); In order to harness the transversal dipole modulation of the core towards Ps modulation, we synthesized a second generation of chiral thioindigo dopants with additional polar substituents at the 5,5{dollar}spprime{dollar} positions, e.g. (R,R)-1b, -1c, which provide the necessary steric coupling with the chiral side-chains. As a dopant in a S{dollar}sb{lcub}rm C{rcub}{dollar} host, R,R)-1b caused Ps to increase by ca. 85% upon trans-cis photoisomerization at 514 nm, while (R,R)-1c caused Ps to increase by ca. 300% upon trans-cis photoisomerization at 532 nm. Control experiments showed that Ps photomodulation is achieved without destabilization of the S{dollar}sb{lcub}rm C{rcub}{dollar} layers. The prototype of a FLC optical switch based on photoinduced Ps sign reversal using dopant (R,R)-1c has been built and tested.
机译：铁电液晶（FLC）是手性近晶C（S {dollar} sb {lcub} rm C {rcub} sp *）{dollar}相，表现出自发极化（Ps）。永久偶极矩是分子手性的宏观表现。在交叉偏振器之间，FLC通过使用施加的电场切换Ps的方向而成为光阀。由于FLC光阀具有双稳性，因此在没有电场的情况下，写入此类设备的任何数字信息都可以无限期保存。如果FLC介质具有光响应性，则也可以通过光学方式实现Ps方向的切换。因此，可以开发一种可擦除的光存储器件。光学寻址的FLC光阀是基于Ps通过所谓的光机械效应的光调制而开发的，其作用原理是使用在光谱的UV区吸收的偶氮苯掺杂剂使FLC相不稳定。在本文所述的工作中，我们提出以下方法：通过调制手性硫靛蓝掺杂剂的横向偶极矩来光调制铁电液晶的自发极化。当在光谱的可见光范围内照射时，该掺杂剂经历可逆的顺反异构化，并以两种异构体形式保持棒状形状。在该项目的第一部分中，我们合成了一系列的6,6-二烷氧基硫靛蓝掺杂剂，并测试了它们在各种S $ dollar和向列型液晶中的溶解性。基于这些结果，我们合成了在S {dollar} sb {lcub} rm C {rcub} {dollar}宿主中具有更高溶解度的首个手性硫靛蓝掺杂剂（R，R）-1a。将该化合物掺杂在苯甲酸苯酯S {dollar} sb {lcub} rm C {rcub} sp * {dollar}主体中，以诱导铁电S {dollar} sb {lcub} rm C {rcub} sp * {dollar}相并通过辐照引起顺-顺式光异构化，由于硫代靛蓝核心与手性侧链之间不存在空间偶联，导致Ps的光调节作用微不足道。（图，表或图形省略...请参见DAI）；为了将核的横向偶极调制用于Ps调制，我们合成了第二代手性硫代靛蓝掺杂剂，在5,5 {dollar} spprime {dollar}位置具有额外的极性取代基，例如（R，R）-1b，-1c，其与手性侧链提供必要的空间偶联。作为S {dollar} sb {lcub} rm C {rcub} {dollar}宿主中的掺杂剂，R，R）-1b导致Ps增加约。在514 nm处反式-顺式光异构化时为85％，而（R，R）-1c导致Ps约增加。在532 nm处反式-顺式光异构化时为300％。对照实验表明，实现了Ps光调制，而没有使S {dollar} sb {lcub} rm C {rcub} {dollar}层不稳定。已经建立并测试了基于使用掺杂剂（R，R）-1c的光致Ps符号反转的FLC光开关的原型。

著录项

  • 作者

    Dinescu, Liviu.;

  • 作者单位

    Queen's University at Kingston (Canada).;

  • 授予单位 Queen's University at Kingston (Canada).;
  • 学科 Chemistry Organic.; Physics Optics.; Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 1998
  • 页码 150 p.
  • 总页数 150
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 有机化学;光学;无线电电子学、电信技术;
  • 关键词

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