Liquid Crystal Surfaces and Symmetry

表面上的手性可以对界面附近的各种性质产生重要影响，甚至可以通过长程色散/弹性相互作用在体中产生重要影响。对于液晶（lc）来说尤其如此。基于Rosenblatt最近的技术发展，既可以在纳米尺度上成像LC取向，又可以使用固有的非手性对准材料在表面上创建受控的手性，他建议研究手性定位在表面附近的LC现象，其“强度”甚至被迫沿着表面在空间上变化。由材料研究部凝聚态物理和固态和材料化学项目支持的拟议工作有几个目标，这些目标由界面上的手性及其对LCs的影响这一共同主题相互关联。要解决的问题包括：手性如何影响LC在基底上的锚定，特别是相互作用势的表面自由能膨胀中奇阶（线性、三次等）项的出现；手性取向层如何在界面附近的外消旋LC混合物中诱导对映体分离，以及这种分离发生的空间范围；手性取向层（可变厚度）如何以及在多大程度上将其手性转化为非手性LC；手性胶包体对LC整体手性的影响。通过利用PI从非手性材料中创建强度可控的手性基底的能力，以及他在共聚焦显微镜的1/1000体积尺度上成像LC取向的能力，这项工作将改变我们对表面手性及其对各向异性流体影响的概念和方法。为了完成提出的目标，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层析成像，原子力显微镜，椭偏术，光刻和各种电光技术。手性是缺乏镜像对称性，即无法通过旋转和平移将物体叠加到其镜像上。一个人的左手和右手是手性的，因为它们互为镜像；这就是“手性手性”一词的起源。手性在大尺度和小尺度系统中都起着核心作用。在大范围内，机械螺丝等技术可以追溯到古代。在微观和纳米尺度上，手性在物理、化学、生物和医学中起着核心作用，对生命的存在至关重要（例如，DNA是手性的）。虽然手性通常被认为是三维的，但它也可以以准二维现象的形式存在于一个表面上：例如，考虑一个多转或多臂螺旋。在这项由凝聚态物理和固态与材料化学项目支持的工作中，Rosenblatt将在纳米尺度的表面上机械地创造手性图案，并将使用液晶（lc）来探索如何控制手性的“强度”，手性如何传递到非手性分子中，如何分离相反“手性”的分子（特别是药物），并发现新的有用的电光现象，这些现象可以从局限于表面附近狭窄区域的手性中推断出来。学生培训是该方案的重要组成部分。PI的学生——博士后、研究生、本科生和高中生——在团队中工作，他们的成果将被纳入本科和研究生水平的课程。此外，他们将与PI的国际合作伙伴互动，包括意大利的<s:1>德拉卡拉布里亚大学，法国的皮埃尔和玛丽居里大学，以及日本的长冈工业大学，同时加强我们的技术基础设施：这些学生最终将加入PI以前的学生和博士后，他们现在活跃在IBM、摩托罗拉、Teledyne、英特尔和苹果电脑等实验室的研发领域，并在美国和世界各地的大学担任教职。

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&amp;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.