Liquid Crystal Surfaces and Symmetry

液晶表面和对称性

• 批准号: 1065491
• 负责人: Charles Rosenblatt
• 金额: $ 40万
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-11-01 至 2015-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1065491&HistoricalAwards=false
• 关键词: Liquid; Crystal; Surfaces; Symmetry

TECHNICAL SUMMARY Chirality at a surface can have important consequences on a wide variety of properties near an interface, and even in the bulk via long range dispersive/elastic interactions. This is especially true of liquid crystals (LCs). Based on Rosenblatt's recent development of techniques both to image LC orientation on nanoscopic length scales and to create controlled chirality at surfaces using inherently achiral alignment materials, he proposes to examine LC phenomena in which chirality is localized near a surface - and whose "strength" is even forced to vary spatially along the surface. The proposed work supported by the Condensed Matter Physics and Solid State and Materials Chemistry Programs in the Division of Materials Research has several objectives interconnected by the common theme of chirality localized to an interface and its effect on LCs. Among the issues to be addressed are: how chirality affects the anchoring of a LC at a substrate, especially the appearance of odd order (linear, cubic, etc.) terms in the surface free energy expansion of the interaction potential; how a chiral alignment layer induces enantiomeric resolution in a racemic LC mixture near the interface and the spatial extent over which this segregation occurs; how and to what extent a chiral alignment layer (of variable thickness) transmits its chirality into an otherwise achiral LC; and the effects of chiral colloidal inclusions on the bulk chiral properties of the LC. By exploiting the PI's ability to create chiral substrates of controlled strength from achiral materials and his ability to image LC orientation on volumetric scales 1/1000th that of confocal microscopy, this work will transform our conceptions about, and methodology toward, surface chirality and its effects on anisotropic fluids. To accomplish the proposed goals, the PI, his students, and postdocs will utilize a wide battery of experimental tools, including (but not limited to) traditional optical microscopy and optical nanotomography, atomic force microscopy, ellipsometry, photolithography, and a variety of electrooptic techniques.NON-TECHNICAL SUMMARYChirality is the absence of mirror symmetry, i.e., the inability to superimpose an object onto its mirror image by rotation and translation. One's hands - left and right - are chiral, as they are mirror images of each other; this is the origin of the term "chiral handedness". Chirality plays a central role in both large scale and small scale systems. On large scales, technologies such as the mechanical screw date back to antiquity. On microscopic and nanoscopic scales, chirality plays a central role in physics, chemistry, biology, and medicine, and is crucial for the existence of life (e.g., DNA is chiral). Although chirality most often is thought of as 3D, it also can exist at a surface as a quasi-two-dimensional phenomenon: For example, think of a multi-turn or multi-arm spiral. In this work, supported by the Condensed Matter Physics and Solid State and Materials Chemistry Programs, Rosenblatt will mechanically create chiral patterns on surfaces on nanoscopic length scales, and will use liquid crystals (LCs) to explore how one can control the "strength" of the chirality, how the chirality is transmitted into nonchiral molecules, how to separate molecules (especially pharmaceuticals) of opposite "handedness", and to discover new and useful electrooptic phenomena that can be deduced from chirality confined to a narrow region near a surface. Student training is an essential component of the proposal. The PI's students - postdocs, graduate, undergraduate, and high school students - work in teams, and will see their results incorporated into courses at both the undergraduate and graduate levels. Moreover, they will interact with the PI's international partners the Universitá della Calabria (Italy), Université Pierre et Marie Curie (France), and Nagaoka University of Technology (Japan), with a concomitant enhancement of our technological infrastructure: The students will eventually join the PI's former students and postdocs who now are actively employed in the R&D field at laboratories such as IBM, Motorola, Teledyne, Intel, and Apple Computer, and are faculty members at universities in the U.S. and around the world.

表面处的手性可对界面附近的多种性质具有重要影响，并且甚至在本体中经由长范围色散/弹性相互作用。 这对于液晶（LC）尤其如此。 基于Rosenblatt最近开发的技术，既可以在纳米尺度上成像LC取向，也可以使用固有的非手性排列材料在表面上产生受控的手性，他建议研究LC现象，其中手性位于表面附近-其“强度”甚至被迫沿表面沿着空间变化。 由材料研究部的凝聚态物理学和固态与材料化学计划支持的拟议工作有几个目标，这些目标通过定位于界面的手性及其对LC的影响的共同主题相互关联。 要解决的问题包括：手性如何影响LC在衬底上的锚定，特别是奇数阶（线性，立方等）的出现。相互作用势的表面自由能膨胀中的术语;手性配向层如何在界面附近的外消旋LC混合物中诱导对映体拆分以及这种分离发生的空间范围;手性配向层如何以及在多大程度上诱导对映体拆分。（可变厚度）将其手性传递到另外的非手性LC中;以及手性胶体包裹体对液晶体手性性质的影响。 通过利用PI的能力，创造手性基板的控制强度从非手性材料和他的能力，图像LC取向的体积尺度1/1000的共聚焦显微镜，这项工作将改变我们的概念，和方法走向，表面手性及其对各向异性流体的影响。 为了实现提出的目标，PI，他的学生和博士后将利用广泛的实验工具，包括（但不限于）传统的光学显微镜和光学纳米断层扫描，原子力显微镜，椭圆偏振，光刻，和各种电光技术。非技术概述手性是缺乏镜像对称，即，不能通过旋转和平移将物体复制到它的镜像上。 一个人的手-左手和右手-是手性的，因为它们是彼此的镜像;这是术语“手性”的起源。 手征性在大尺度和小尺度系统中都起着核心作用。 在大规模上，机械螺钉等技术可以追溯到古代。 在微观和纳米尺度上，手性在物理学、化学、生物学和医学中起着核心作用，并且对于生命的存在至关重要（例如，DNA是手性的）。 虽然手征性通常被认为是3D的，但它也可以作为准二维现象存在于表面上：例如，考虑多圈或多臂螺旋。 在这项工作中，由凝聚态物理和固态与材料化学计划支持，Rosenblatt将在纳米尺度的表面上机械地创建手性图案，并将使用液晶（LC）来探索如何控制手性的“强度”，如何将手性传递到非手性分子中，如何分离分子（特别是药物）相反的“手性”，并发现新的和有用的电光现象，可以推导出从手性局限于一个狭窄的区域附近的表面。 学生培训是该提案的一个重要组成部分。 PI的学生-博士后，研究生，本科生和高中生-在团队中工作，并将看到他们的结果纳入本科和研究生课程。 此外，他们将与PI的国际合作伙伴卡拉布里亚大学（意大利），皮埃尔和玛丽居里大学（法国）和长冈工业大学（日本）进行互动，同时加强我们的技术基础设施：学生最终将加入PI的前学生和博士后，他们现在积极从事&IBM，摩托罗拉，Teledyne，英特尔，和苹果电脑，并在美国和世界各地的大学教员。