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Study on Smectic Liquid Crystalline Structure in Main-Chain Polyester

主链聚酯层列液晶结构的研究

基本信息

批准号：
01550688
负责人：
WATANABE Junji
金额：
$ 1.09万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

The thermotropic liquid crystal nature of mainーchain polyesters that can be constructed by an alternative arrangement of the p,p'ーbibenzoate unit as a mesogenic group and the alkanediol as a flexible spacer. The polyesters are designated BB-n where n is the number of methylene units in the diol. This homolog ous series of BB-n (n = 3-9) invariably form smectic mesophases whose isotropization temperatures and entropies exhibit an evenーodd oscillation with the number of intervening methylene units, n. The evenーodd nature of the methylene unit also reflected the thickness of smectic layers, with a larger layer thickness in the even series. Comparing the observed thickness with the calculated ones based on the rotational isomeric state model, we concluded that the evenーodd nature is strongly related to the polymer chain conformations and that the different types of smectic structures can be formed between the two. In even numbered polyesters there is formed a normal smectic A phase in which both axes of the polymer chain and mesogenic group lie perpendicular to the layers. In oddーnumbered ones, in contrast, the smectic structure was found to be a type of smectic C in which the average chain axis of the polymer is perpendicular to the layer, but the mesogenic groups are tilted with respect to the layer normal. Such structural characteristics are also confirmed from the xーray and optical microscopic studies for the oriented smectic phases.

主链ー聚酯的热致液晶性质，可通过交替排列p，p‘ー联苯甲酸酯单元作为介晶基团和烷基二醇作为柔性间隔基来构建。聚酯被命名为BB-n，其中n是二元醇中的亚甲基单元的数目。BB-n(n=3-9)的同质系列总是形成近晶介相，其各向同性温度和各向同性熵随亚甲基单元个数n呈现ー奇数振荡。亚甲基单元的奇偶ー性质也反映了近晶层的厚度，在偶数系列中具有较大的层厚度。将观察到的厚度与基于旋转同分异构态模型计算的厚度进行比较，我们得出结论：偶ー奇性与高分子链构象密切相关，并且两者之间可以形成不同类型的近晶结构。在偶数聚酯中，形成了一个正常的近晶A相，其中聚合物链和介晶基团的轴线都垂直于层。相反，在奇数ー数中，近晶结构是一种近晶C，其中聚合物的平均链轴垂直于层，但介晶基团相对于法层倾斜。这种结构特征也从取向近晶相的X-ー射线和光学显微镜研究中得到证实。