Vitrified Liquid Crystalline Films: Material Synthesis and Optical Properties

摘要-9818234 S。H.陈U。液晶介晶性的特征在于单轴（即层状）、层状（即近晶）、螺旋状（即螺旋状）或柱状（即柱状）。e.通过自组装实现分子的无序排列。 由于其独特的光学性质，液晶（LC）已经在电光和光电子学中找到了各种既定的和潜在的应用。 在现在几乎成熟的LC显示器技术中，LC材料在流体状态下起作用，其中施加的场以毫秒级的响应时间诱导分子取向。 通过明智设计的结构部分，LC也可以经由光子或电子刺激以固态起作用，其响应时间为皮科或飞秒量级。 除了这些开关器件之外，薄膜中的LC可以用作非开关器件（例如，用于偏振光学器件）。 除了涉及分子取向动力学的应用外，具有高于环境玻璃化转变温度的玻璃化LC膜特别适合于制造环境稳健的设备。 本研究的主要内容是玻璃化液晶的制备，主要包括两种互补的方法：玻璃发泡液晶（glass-foaming liquid crystals，GLC）和交联液晶聚合物（crosslinked LC polymers，XLCPs），目的是将材料加工成宏观有序的固体薄膜。在美国国家科学基金会（NSF）的一个项目中，已经成功地制备出了具有上级形态稳定性的高光学双折射玻璃化液晶。 为了利用这类新出现的有机材料，将设计和合成低至300 nm透明的GLC，用于单轴和螺旋取向的发光体以产生偏振光。 作为一种补充材料概念，将对具有类似特性的XLCP进行比较研究。 在这种方法中，在流体状态下实现的高度分子有序性将通过光诱导聚合和交联来保持。 除了非线性材料，新的方法，梯度间距手性非线性GLC和XLCPs将探索广泛的调查偏振光致发光，包括共振区，没有以前的尝试。 通过考虑周期性结构薄膜中的光吸收、发射和传播，将构建一个全面的圆偏振光致发光理论。 一般的理论将减少到线性偏振光致发光（从玻璃化手性荧光膜中的单轴排列的发光体和圆二色性/圆偏振（从玻璃化手性荧光膜中的光吸收和传播）作为两个极限情况。 将进行实验来量化偏振度，以验证理论预测。 在高效率偏振、偏振光发射、彩色投影、立体显示和分布反馈激光器等方面的潜在应用也将被探索。 总之，偏振光对于光学信息处理、显示和存储至关重要。 提出的研究旨在使用发光和非发光薄膜产生偏振光。 根据拟议的计划，新一代科学家和工程师将在多学科环境中接受教育。 新的原则将建立描绘光学过程中宏观有序的薄膜和发展上级材料有助于光学信息技术的进步。

ABSTRACTCTS-9818234S. H. ChenU. of RochesterLiquid crystalline mesomorphism is characterized by a unaxial (i.e. nematic), lamellar (i.e. smectic), helical (i.e. cholesteric), or columnar (i. e. discotic) arrangement of molecular through self-assembly. Because of their unique optical properties, liquid crystals (LCs) have found various established and potential applications to electro-optics and optoelectronics. In the now almost mature LC display technology, LC materials function in the fluid state where an applied field induces molecular orientation with a response time on order of milliseconds. With judiciously designed structural moieties, LCs may also function in the solid state via a photonic or electronic stimulus with a response time on the order of pico- or femtoseconds. In addition to these switching devices, LCs in thin films can be employed as nonswitching devices (e.g. for polarization optics). With the exception of applications where the dynamics of molecular orientation are involved, vitrified LC films with an above-ambient glass transition temperature are uniquely suited for the fabrication of environmentally robust devices. The main theme of the proposed research is on vitrified LCs following two complementary approaches: glass-foaming liquid crystals (GLCs) and crosslinked LC polymers (XLCPs), with the objective of facilitating material processing into macroscopically ordered solid films.Capable of vitrification into well-ordered films with superior morphological stability, high optical birefringence GLCs have been successfully developed under a current NSF project. To take advantage of this new emerging class of organic materials, GLCs transparent down to 300 nm will be designed and synthesized for uniaxially and helically orienting luminophores to generate polarized light. As a complementary material concept, XLCPs of similar characteristics will be pursued for a comparative study. In this approach, the high degree of molecular order achieved in the fluid state will be preserved via photoinduced polymerization and crosslinking. In addition to nematic materials, novel approaches to gradient-pitch chiral-nematic GLCs and XLCPs will be explored for an extensive investigation of polarized photoluminescence, including the resonance region where no prior attempts have been made. A comprehensive theory will be constructed for circularly polarized photoluminescence by considering light absorption, emission, and propagation in periodically structured films. The general theory will be reduced to linearly polarized photoluminescence (from uniaxially aligned luminophores in vitrified nematic films and circular dichrosim/circular polarization (from light adsorption and propagation in vitrified chiral-nematic films) as two limiting cases. Experiments will be conducted to quantify the degrees of polarization for a validation of theoretical predictions. Potential applications to high-efficiency polarization, polarized light emission, color projection, stereoscopic display, and distributed feedback laser ill also be explored. In summary, polarized light is essential to optical information processing, display, and storage. The proposed research aims at the generation of polarized light using light-emitting and nonemitting films. Under the proposed program, a new generation of scientists and engineers will be educated in a multidisciplinary setting. New principles will be established for delineating optical processes in macroscopically ordered films and for developing superior materials instrumental to the advancement of optical information technologies.