Magnetic Resonance Studies of Order and Dynamics in Liquid- Crystalline Polymers

液晶聚合物有序和动力学的磁共振研究

• 批准号: 9420458
• 负责人: Cynthia Jameson
• 金额: $ 18.5万
• 依托单位: University of Illinois at Chicago
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-01-15 至 1998-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9420458&HistoricalAwards=false
• 关键词: Magnetic; Resonance; Studies; Order; Dynamics

9420458 Frydman This project focuses on nuclear magnetic resonance investigation of order and dynamics in liquid-crystalline polymers. These new materials play special roles in several structural and electronic applications. Their main characteristics are a strong affinity towards the formation of liquid-crystalline solutions, and an ability to retain these solution arrangements upon going into the solid state. This combination makes possible the generation of highly ordered macromolecular materials with valuable mechanical, thermal and non-linear optical properties. Further advances in the practical utilization of these polymers are intimately linked to understanding the ways in which chemical structures and external factors such as flow fields, can control their dynamics and orientations. These aspects are explored using state-of-the-art multidimensional nuclear magnetic resonance in both the liquid-crystalline and the solid phase, as well as gradient-based magnetic resonance microscopy methods. These experiments rely extensively on a specialized technology whose purpose is the characterization of local anisotropic environments at molecular and supramolecular levels. They involve the use of high-temperature dynamic-angle assemblies for studying molten thermotropics, of variable-angle spinning probeheads for solid-phase analyses of order and reorientations, and of rheo-imaging instrumentation for the investigation of flow in lyotropics. Using these techniques it will be possible to probe how local mesomorphic order in thermotropic liquid- crystals depends on chemical composition; how much of the liquid-crystalline order of these systems is preserved upon cooling them into glasses; how solid-phase chain dynamics affect the alignment of these polymeric glasses and what is their exact nature; and how different types of flow and diffusion impart a net anisotropy of solutions of liquid- crystalline polymers. An important aspect of these experiments is the ir reliance on the natural-abundance observation of 13C spins, a method that imposes no preconditions on the type or origin of the samples under study. Thus, the materials to be analyzed include homopolyesters with high melting temperatures, commercial thermotropic copolymers, complex molecular blends of liquid- crystalline and random polymers, and corrosive lyotropic solutions. %%% All these are highly relevant systems, whose better understanding should have a significant impact on their practical application.

9420458 Frydman该项目侧重于液晶聚合物中有序和动力学的核磁共振研究。 这些新材料在一些结构和电子应用中发挥着特殊的作用。 它们的主要特征是对形成液晶溶液的强亲和力，以及在进入固态时保持这些溶液排列的能力。 这种组合使得有可能产生具有有价值的机械，热和非线性光学性能的高度有序的大分子材料。 这些聚合物在实际应用中的进一步进展与理解化学结构和外部因素（如流场）可以控制其动力学和取向的方式密切相关。 这些方面的探索使用最先进的多维核磁共振在液晶和固相，以及基于梯度的磁共振显微镜方法。 这些实验广泛依赖于一种专门的技术，其目的是在分子和超分子水平上表征局部各向异性环境。 它们涉及使用高温动态角组件研究熔融热致性，可变角度旋转探头的顺序和重取向的固相分析，和流变成像仪器的流动溶致性的调查。 使用这些技术，将有可能探测热致液晶中的局部介晶有序如何取决于化学组成;这些系统在冷却成玻璃时有多少液晶有序被保留;固相链动力学如何影响这些聚合物玻璃的排列以及它们的确切性质是什么;以及不同类型的流动和扩散如何赋予液晶聚合物溶液的净各向异性。 这些实验的一个重要方面是依赖于13 C自旋的自然丰度观测，这种方法对所研究样品的类型或来源没有任何先决条件。 因此，待分析的材料包括具有高熔融温度的均聚酯、商业热致共聚物、液晶和无规聚合物的复杂分子共混物以及腐蚀性溶致溶液。 %所有这些都是高度相关的系统，更好地理解它们应该对它们的实际应用产生重大影响。