Optical and Resonant X-Ray Diffraction Studies of Nano-Scale Orientation Order in Liquid Crystals

液晶纳米级取向顺序的光学和共振 X 射线衍射研究

• 批准号: 0605760
• 负责人: Cheng-Cher Huang
• 金额: $ 44万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-11-15 至 2011-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0605760&HistoricalAwards=false
• 关键词: Optical; Resonant; Ray; Diffraction; Studies

This project focuses on (1) understanding the nature of relevant phase transitions, (2) determining the underlying intermolecular ordering and interactions in the liquid crystal phases, and (3) studying thin free-standing films to observe two-dimensional and surface phenomena. Experimental results shed new light into the fundamentals of molecular packing in various liquid crystal phases and provide theorists with important physical parameters for theoretical advances. Chiral smectic liquid-crystals are an important class of liquid crystals. Thus far resonant x-ray diffraction (RXRD) has been the most powerful experimental probe to obtain the nano-scale molecular orientational order. Expanding the use of this probe, RXRD is being applied to binary mixtures (AxB1-x) with x = 0.10. Here the compound A has a heavy element (e.g., sulfur) in the core part of the molecule, while the compound B does not. An important breakthrough, the use of binary mixtures has greatly enhanced experimental capabilities. Table-top optical probes are irreplaceable in-house experimental tools to acquire essential information before and after RXRD runs. With the need to manufacture high speed electro-optical switching devices and with a new interest in special materials to be employed in optic fiber networks, the characterization of exotic liquid crystal mesophases capable of such applications is critically important. Liquid crystal mesophases show both liquid- and crystal-like order. Some compounds display a series of phase transitions (five or more mesophases) in a relatively small temperature window (~30o F). They provide a novel system to explore the richness of structures and molecular packing of many organic molecules. This project will provide unique opportunities to train both undergraduate and graduate students in designing and constructing state-of-the-art optical and x-ray diffraction systems as well as acquiring, analyzing and understanding high quality experimental data.

该项目的重点是（1）理解相关相变的性质，（2）确定液晶相中的潜在分子间有序和相互作用，以及（3）研究薄的独立膜以观察二维和表面现象。实验结果揭示了新的光在各种液晶相的分子堆积的基本原理，并提供理论家的理论进展的重要物理参数。手性近晶液晶是一类重要的液晶。共振X射线衍射（RXRD）是迄今为止获得纳米尺度分子取向有序性的最有力的实验探针。扩展了这种探头的使用，RXRD被应用于二元混合物（AxB 1-x），x = 0.10。这里化合物A具有重元素（例如，硫）在分子的核心部分，而化合物B没有。一个重要的突破，使用二元混合物大大提高了实验能力。台式光学探头是不可替代的内部实验工具，可在RXRD运行前后获取重要信息。随着对高速电光开关器件的需求和对光纤网络中所用特殊材料的新兴趣，能够用于此类应用的奇异液晶中间相的表征是至关重要的。 液晶中间相表现出液晶和类晶有序。一些化合物在相对较小的温度窗口（~ 30 ° F）中显示出一系列相变（五个或更多个中间相）。它们提供了一个新的系统来探索许多有机分子的丰富结构和分子堆积。该项目将提供独特的机会，培养本科生和研究生设计和构建最先进的光学和X射线衍射系统，以及获取，分析和理解高质量的实验数据。