Helical Structure and Supramolecular Structure of Cellulose Derivatives in Solution

在本研究项目中，我们研究了纤维素衍生物三(苯基氨基甲酸酯)(CTC)浓缩液的溶液局部构象、液晶度和动力学性质(粘度和扩散)。研究结果如下：(1)从以往的构象能计算得知，纤维素链上的每个葡萄糖残基都有两个能量稳定的构象(一个左旋3/1螺旋和扩展的2/1螺旋)。从温度和分子质量对特性粘度的依赖关系出发，研究了纤维素链在溶液中的局部构象。(2)确定了CTC溶液形成胆甾相的临界浓度是分子量的函数。与硬链聚合物溶液的统计力学理论进行了比较。(3)测定了CTC溶液从稀释到浓缩区的零剪切粘度随CTC相对分子质量和浓度的变化关系。用动态光散射法和脉冲场梯度核磁共振法分别测量了四氢呋喃溶液的自扩散系数和互扩散系数。与模糊圆柱体理论相比，后者的系数更接近于模糊圆柱体理论。(5)随着聚合物浓度的增加，CTC的胆甾相THF溶液转变为胆固相凝胶，然后胆甾相的颜色消失。开始了这种凝胶化行为的初步实验。

In this research project, we have investigated the local conformation in solution, liquid crystallinity and dynamic properties (viscosity and diffusion) of concentrated solutions for a cellulose derivative, cellulose tris(phenyl carbamate) (CTC). The research results are as follows.(1) It is know that each glucose residue in the cellulosic chain takes two energetically stable conformations (a left-handed 3/1 helix and extended 2/1 helix) from previous conformation energy calculations. The local conformation of the cellulosic chain in solution was investigated from the temperature and molecular weight dependencies of the intrinsic viscosity.(2) The critical concentration for the cholesteric phase formation for concentrated THE solutions of CTC was determined as a function of the molecular weight. The results were favorably compared with a statistical mechanical theory for stiff-chain polymer solutions.(3) Zero-shear viscosities of THE solutions of CTC from dilute through concentrated regime were measured as functions of the molecular weight and concentration of CTC. The results were favorably compared with a theory for polymer dynamics (the fuzzy cylinder theory) for stiff-chain polymer solutions(4) The mutual-and self-diffusion coefficients for THF solutions of CTC was measured up to a concentrated regime by dynamic light scattering and pulse-field gradient NMR, respectively. While the latter coefficient was favorably compared with the fuzzy cylinder theory, the former coefficient was not.(5) Cholesteric THF solutions of CTC were trartsformed into cholesteric gels and then the cholesteric color was disappeared with increasing the polymer concentration. A preliminary experiment for this gelation behavior was started.