碗型化合物中间相的X射线衍射研究

本文通过X射线衍射分析,发现两种碗型化合物呈现无序晶相(一种有序中间相),它们有长程位置有序,但分子的位置和取向有强烈的扰动,同时分子的支链处于熔融态。实验表明该相为三斜晶系,空间群为Pl,并给出了晶格参数、密度以及膨胀系数等。本文提出了其晶胞内分子的堆垛方式。结论表明,碗型分子没有“上”、“下”对称性,宏观上也没有铁电性。关键词：

AN X-RAY STUDY OF MESOPHASE OF BOWL-LIKE COMPOUNDS

We have found that some bowl-like compounds can form disordered crystalline phaseswhich have long-range positional order, with strong fluctuation in position and orientation. Their side chains are in a molten state. X-ray diffraction has shown that two homologues of hexaesters of cyclotricatechylene are stacked as triclinic system with space group of Pl. The parameters of a unit cell, density of the compounds, as well as expansion coefficient are obtained. The modelling of an unit cell is presented, which confirms the up and down asymmetry in the molecules, but there is no ferroelectricity macroscopically.