Generation of biaxiality in smectic A phases by introduction of intermolecular perfluoroarene–arene and C–H/F interactions, and the non-odd–even effect of the molecules in their transition temperatures and layer distances
作者:Keiki Kishikawa、Takahiro Inoue、Yoshiyuki Sasaki、Sumihiro Aikyo、Masahiro Takahashi、Shigeo Kohmoto
DOI:10.1039/c1sm05887h
日期:——
Compounds 1aâj, 4-alkoxy-4â²-pentafluorobenzoyloxybiphenyls, were synthesized to investigate the biaxiality in the smectic A phases of rod-like molecules possessing both perfluorinated and non-fluorinated benzene rings. The phase behaviors of the compounds and the molecular packing structures of their smectic A phases were investigated by polarized optical microscopy (POM), differential scanning colorimetry (DSC), and X-ray diffraction (XRD). As a result, it was found that the plot of the transition temperatures against the number of carbon atoms in the terminal alkyl chains did not show a clear oddâeven effect, and an unique effect âtgg-effectâ was observed in the plots of their layer distances against the number of carbon atoms. In the detailed 1D- and 2D-XRD studies of the smectic A phases, lateral directional orders in each layer were observed. It is assumed that these results originate from the biaxiality of the smectic A phases and slow rotation of the molecules around their molecular long axes.
化合物1a–j,即4-烷氧基-4′-五氟苯甲酸氧基联苯,被合成用于研究具有全氟化和非氟化苯环的棒状分子在液晶A相中的双轴性。通过偏光显微镜(POM)、差示扫描量热法(DSC)和X射线衍射(XRD)研究了这些化合物的相行为及其液晶A相的分子排列结构。结果发现,过渡温度与末端烷基链中碳原子数的图示并未显示出明显的奇偶效应,而在层间距与碳原子数的图示中观察到一个独特的“tgg效应”。在液晶A相的详细一维和二维X射线衍射研究中,观察到每一层中的横向方向有序性。这些结果被认为是源于液晶A相的双轴性以及分子绕其长轴的缓慢旋转。