Polarizations and Symmetries in Liquid Crystals

所提出的工作的目的是研究液晶的对称性相关行为。具体来说，这些研究旨在增加对手性和对称性如何影响液晶行为的理解。本课程将研究与铁电及反铁电液晶有关的各种现象，包括电斜效应的动力学、铁电液晶中低频二次谐波的产生、空间周期极化、反铁电-“无序”相变的行为，以及反铁电-铁电相变。对称破碎表面对液晶极化的影响将被探讨。铁电液晶的相关研究也将进行，包括离子吸附和对映体浓度波动的研究。最后，将探索一个涉及受限几何形状液晶的新推力领域，特别关注与手性液晶相关的宿主矩阵的大表面体积比的作用。将使用一系列实验工具，包括静态和动态光散射、介电弛豫、磁和电双折射以及其他电光测量、磁化率测量和fredericksz技术。本研究旨在加深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，人们发现在近晶层的平面上存在宏观极化。在对称破缺界面处存在一个垂直于表面的极化；如果分子是手性的，缺乏反转对称性，并且相对于界面是倾斜的，那么额外的极化分量可能存在于并平行于界面e。手性也可能影响相转变的性质，或者引入全新的相，如蓝色相。拟议的研究将提供对这些现象的更深入的基本理解，它也可能影响技术基础设施。先前拨款下的工作产生了一种新的显示技术；在拟议的研究下进行的工作结果有可能影响当前的科学和技术思维，并可能对显示行业产生影响。

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.