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

各向异性相中柔性链的构象和有序问题近年来引起了人们的广泛关注。大多数这项工作的动机是想要了解烷基链挂在芳香核影响介晶相性质和稳定性的方式。液晶聚合物作为高拉伸强度纤维和涂层的可能来源，以及它们在电光器件中的可能应用，也一直是研究的主题。虽然具有刚性骨架的聚合物通常不会形成液晶相，也不会在熔化成记忆相之前分解，但在聚合物骨架中引入柔性间隔链会将中间相转变温度降低到热分解范围以下。氘核磁共振光谱已经成为探测末端链和间隔链微观结构和动力学以及测试链在向列相中有序模型的主要工具。Drobny教授提出了一种使用多重量子光谱学研究向列相和低温中间相中间隔层和端链排序的方法。而不是测试链的有序和构象模型，构象概率和有序张量元将直接计算从多个量子光谱得到的质子-质子和质子-碳偶极耦合。

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.