Proton Multiple Quantum NMR Studies of Space and End Chain Conformation in Liquid Crystals

液晶空间和端链构象的质子多量子核磁共振研究

基本信息

批准号：
8700081
负责人：
Gary Drobny
金额：
$ 24万
依托单位：
University of Washington
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
1987
资助国家：
美国
起止时间：
1987-06-01 至 1990-11-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=8700081&HistoricalAwards=false
关键词：
Proton Multiple Quantum NMR Studies

项目摘要

The problem of the conformation and ordering of flexible chains in anisotropic phases has attracted a good deal of attention in recent years. The motivation of most of this work is a desire to understand the manner in which alkyl chains pendant to aromatic cores influence mesomorphic phase properties and stability. Liquid crystal polymers have also been the subject of research as possible sources of high tensile strength fibers and coatings, and for their possible applications in electro-optic devices. Although polymers with rigid backbones do not generally form liquid crystalline phases, or decompose before melting into memorphic phases, the introduction of flexible spacer chains into the polymer backbone will lower mesophase transition temperatures to below the range of thermal decomposition. Deuterium NMR spectroscopy has been the principal tool for probing the microscopic structure and dynamics of end and spacer chains, and for testing models of chain ordering in nematic phases. Professor Drobny proposes an approach to studying spacer and end chain ordering in the nematic phase and in several in low temperature mesophases using multiple quantum spectroscopy. Rather than test models of chain ordering and conformation, conformational probabilities and order tensor elements will be directly calculated from proton-proton and proton-carbon dipolar couplings obtained from multiple quantum spectra.

近年来，各向异性阶段中柔性链的构象和顺序的问题引起了很多关注。大多数这项工作的动机是渴望了解芳族岩心悬挂式烷基链的方式影响介导相的特性和稳定性。液晶聚合物也已成为研究的主题，作为高抗拉力纤维和涂料的可能来源，以及它们在电磁设备中的可能应用。尽管具有刚性骨架的聚合物通常不会形成液晶相，或者在融化成纪念相之前分解，但将柔性间隔链引入聚合物骨架中的聚合物将降低降低的介体过渡温度至低于热分解范围。 NMR光谱学仅是探测末端和间隔链的显微镜结构和动力学的主要工具，以及在nematic阶段测试链排序模型的主要工具。 Drobny教授提出了一种在列中使用多个量子光谱法研究夜间阶段的间隔和终端链排序的方法。构象概率和量张量元件将直接根据质子 - 原质子和质子 - 碳偶极耦合直接计算，而不是链排序和构象的测试模型，而是从多个量子光谱中直接计算出来。