Polarizations and Symmetries in Liquid Crystals

小行星9502825 本文的目的是研究液晶的对称性相关行为.具体而言，调查的目的是增加了解如何手性和对称性影响液晶行为。与铁电和反铁电液晶相关的各种现象将被研究，包括电斜效应的动力学，铁电液晶中的低频二次谐波产生，空间周期性极化，反铁电-“无序”相变的行为，以及反铁电-铁电相变。将探讨与液晶偏振相关的破膜表面的影响。同时也将进行铁电液晶的相关研究，包括离子吸附和对映体浓度波动的研究。最后，一个新的推力领域，涉及液晶在受限的几何形状将进行探索，特别注意的作用，大的表面积与体积比的主机矩阵，因为它涉及到手性液晶。一组实验工具将被使用，包括静态和动态光散射，介电弛豫，磁和电双折射和其他电光测量，磁电阻测量，和Freedericksz技术。 这项研究旨在增加对手性和对称性如何影响液晶行为的理解。对称性在液晶行为中起着重要的作用。例如，在由手性分子组成的近晶C相中，在近晶层的平面中发现宏观偏振。在破缺界面处，存在垂直于表面的偏振;如果分子是手性的，缺乏反转对称性，并且相对于界面倾斜，则偏振的附加分量可能存在于界面处并平行于界面。手征也可能影响相变的性质，或引入全新的相，如蓝相。拟议的研究将提供对这些现象的更深入的基本理解，也可能影响技术基础设施。在先前资助下的工作导致了一种新的显示技术;在拟议研究下进行的工作结果有可能影响当前的科学和技术思想，并可能对显示器行业产生影响。

9502825 Rosenblatt The purpose of the proposed work is to investigate symmetry- related behavior of liquid crystals. Specifically, the investigations are designed to increase the understanding of how chirality and symmetry affect liquid crystalline behavior. A variety of phenomena related to ferroelectric and antiferroelectric liquid crystals will be studied including the dynamics of the electroclinic effect, low frequency second harmonic generation in ferroelectric liquid crystals, spatially periodic polarizations, the behavior of the antiferroelectric -"disordered" phase transition, and the antiferroelectric - ferroelectric phase transition. The effects of symmetry-breaking surfaces as they relate to liquid crystalline polarizations will be probed. Related investigations on ferroelectric liquid crystals will also be performed, including studies of ionic adsorption and enantiomeric concentration fluctuations. Finally, a new thrust area involving liquid crystals in confined geometries will be explored, with special attention paid to the role of the large surface-to-volume ratio of the host matrix as it relates to chiral liquid crystals. A battery of experimental tools will be used, including static and dynamic light scattering, dielectric relaxation, magnetic and electric birefringence and other electrooptic measurements, magnetic susceptometry, and Freedericksz techniques. %%% This research is designed to increase the understanding of how chirality and symmetry affect liquid crystalline behavior. Symmetry plays an important role in liquid crystalline behavior. In a smectic C phase composed of chiral molecules, for example, one finds a macroscopic polarization in the plane of the smectic layers. At a symmetry-breaking interface there exists a polarization normal to the surface; if the molecules are chiral, lack inversion symmetry, and are tilted with respect to the interface, an additional component of polarization may reside at and parallel to the interfac e. Chirality may also affect the nature of a phase transition, or introduce entirely new phases such as the blue phases. The proposed research will provide a deeper fundamental understanding of these phenomena, and it may also impact the technological infrastructure as well. Work under the prior grant led to a new display technology; the results of work to be performed under the proposed research have the potential to affect current scientific and technological thinking, and possibly have impact on the display industry as well.