Vitrified Liquid Crystalline Films: Material Synthesis and Optical Properties

摘要-9818234S。H.Chenu.Rochester液晶的特征是分子通过自组装形成单轴(即向列)、片状(即近晶)、螺旋(即胆甾相)或柱状(即盘状)排列。由于其独特的光学性质，液晶在电光和光电子学中得到了广泛和潜在的应用。在现在几乎成熟的液晶显示技术中，液晶材料在流体状态下工作，在这种状态下，外加电场诱导分子取向，响应时间在毫秒数量级。有了精心设计的结构部分，液晶还可以通过光子或电子刺激在固态下工作，响应时间约为皮秒或飞秒。除了这些开关器件外，薄膜中的液晶还可以用作非开关器件(例如，用于偏振光学)。除了涉及分子取向动力学的应用外，玻璃化液晶膜的玻璃化转变温度高于环境玻璃化转变温度，特别适合于制造环保器件。本研究的主要主题是玻璃发泡液晶(GLC)和交联型液晶聚合物(XLCP)两种相互补充的方法，目的是促进材料加工成宏观有序的固体薄膜。在目前的NSF项目下，已经成功地开发出能够玻璃化成具有良好形态稳定性的有序薄膜的高光学双折射液晶。为了利用这一新兴的有机材料类别，将设计和合成透明到300 nm的GLCs，用于单轴和螺旋取向的发光体产生偏振光。作为一个互补的材料概念，具有相似特征的XLCP将被用于比较研究。在这种方法中，通过光诱导聚合和交联会保持在流体状态下获得的高度分子有序性。除了向列型材料外，还将探索梯度间距手性向列型GLC和XLCP的新方法，以广泛研究偏振光致发光，包括以前没有尝试过的共振区。通过考虑光在周期性结构薄膜中的吸收、发射和传播，建立了圆偏振光致发光的综合理论。作为两种极限情况，一般理论将简化为线偏振光致发光(来自玻璃化向列相薄膜中的单轴排列的发光团)和圆二色/圆偏振(来自玻璃化手性向列相薄膜中的光的吸收和传播)。为了验证理论预测，将进行实验来量化偏振度。还将探索其在高效率偏振、偏振光发射、彩色投影、立体显示和分布式反馈激光等方面的潜在应用。总而言之，偏振光对于光学信息处理、显示和存储是必不可少的。这项研究的目的是利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。将建立新的原则，以描述宏观有序薄膜中的光学过程，并开发有助于光学信息技术进步的优良材料。

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.