Rational Design of ferroelectric liquid crystals

铁电液晶的合理设计

• 批准号: 138404-2011
• 负责人: Lemieux, Robert
• 金额: $ 6.19万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=569344
• 关键词: Rational; Design; ferroelectric; liquid; crystals

Chirality is a unique property that many natural and man-made substances and almost all living things possess. Chiral objects exist in right- and left-handed forms (enantiomers), e.g., gloves, shoes and golf clubs, and are non-superposable on their mirror images. Chirality is also manifest at the molecular scale., e.g., amino acids, carbohydrates, and many other natural products. These chiral building blocks assemble via covalent and non-covalent interactions to form larger chiral structures such as proteins and nucleic acids, which themselves assemble into crystalline structures with chiral topographies. Such manifestation of molecular chirality at the macroscopic level, which was first shown by Pasteur in 1848 with sodium ammonium tartrate, is also observed in the chiral smectic C* (SmC*) liquid crystal phase in the form of a ferroelectric polarization (Ps). The polarization of a ferroelectric liquid crystal (FLC) can be coupled to an electric field to produce a fast switching light shutter that can be used in high-resolution display applications. In order to produce FLC films suitable for displays, SmC* liquid crystal mixtures with a minimum amount of chiral material are required. To address this important requirement, our research program focuses on the induction of chirality in smectic phases, and how an axially chiral dopant can propagate its handedness most effectively in a non-chiral SmC host to produce increasingly large polarization powers. This can be achieved by matching the molecular structures of chiral dopants and SmC hosts to maximize chirality transfer via intermolecular interactions. A second aspect of this program focuses on the rational design of SmC liquid crystals that undergo a transition from the non-tilted smectic A (SmA) phase to the tilted SmC phase with minimal layer contraction. Our molecular design strategy is based on achieving a 'frustration' between two structural elements that promote the formation of SmA and SmC phases. These so-called 'de Vries-like' materials will provide a solution to one of the main roadblocks to the use of FLC technology in LCD projectors and large flat panel displays: the formation of zigzag defects caused by layer contraction upon cooling a FLC mixture from the chiral SmA* to the SmC* phase.

手征性是许多天然和人造物质以及几乎所有生物都具有的一种独特性质。 手性对象以右手和左手形式（对映异构体）存在，例如，手套、鞋和高尔夫球杆，并且在它们的镜像上是不可重叠的。 手性在分子尺度上也很明显。例如，在一个实施例中，氨基酸、碳水化合物和许多其他天然产物。这些手性结构单元通过共价和非共价相互作用组装以形成较大的手性结构，例如蛋白质和核酸，其本身组装成具有手性形貌的晶体结构。 这种分子手性在宏观水平上的表现，首先由巴斯德在1848年用酒石酸铵钠显示，也以铁电极化（Ps）的形式在手性近晶C*（SmC*）液晶相中观察到。 铁电液晶（FLC）的极化可耦合到电场以产生可用于高分辨率显示器应用中的快速切换光快门。 为了生产适用于显示器的FLC膜，需要具有最少量手性材料的SmC* 液晶混合物。 为了解决这一重要要求，我们的研究计划集中在近晶相的手性诱导，以及轴向手性掺杂剂如何在非手性SmC主机中最有效地传播其手性，以产生越来越大的偏振功率。 这可以通过匹配手性掺杂剂和SmC主体的分子结构来实现，以通过分子间相互作用最大化手性转移。 该计划的第二个方面侧重于SmC液晶的合理设计，该液晶经历了从非倾斜近晶A（SmA）相到具有最小层收缩的倾斜SmC相的过渡。我们的分子设计策略是基于实现两个结构元素之间的“挫折”，促进SmA和SmC相的形成。这些所谓的“de Vries样”材料将为在LCD投影仪和大型平板显示器中使用FLC技术的主要障碍之一提供解决方案：在将FLC混合物从手性SmA* 冷却到SmC* 相时，由层收缩引起的锯齿形缺陷的形成。