Aromatic polyesters with flexible side chains.: 10.: Studies on biaxiality in nematic liquid crystal of BC-n polyester
Aromatic polyesters with flexible side chains.: 10.: Studies on biaxiality in nematic liquid crystal of BC-n polyester
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DOI：
10.1295/polymj.38.442
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发表时间：
2006-01-01
期刊：
影响因子：
2.8
通讯作者：
Watanabe, Junji
中科院分区：
文献类型：
--
作者：
Fu, Kai;Sone, Masato;Watanabe, Junji
本文报道了均苯四甲酸1，4-二烷基酯和4，4 ′-联苯酚组成的芳香族聚酯BC-n的双轴液晶的可能性。在这些BC-n聚酯中，作为一个总的趋势，芳香族主链和柔性侧链发生微观分离，并在这些层状相熔融后出现双相液晶。取向取向纤维的X射线衍射图除了在赤道线上具有4.5埃的正常外反射外，还具有20埃左右的大间距的异常内反射，表明在垂直于指向矢n的方向上存在两种堆积相关，即存在双轴性。光学显微织构只表现出垂直条纹的垂直条纹= 1/2的双刷向错，也符合双轴向错序。内赤道反射层间距与同同系物形成的层状中间相的层间距相近。这强烈地表明，层状聚集体仍然保留在双相液晶中，其板状形状是双轴性的原因。
This paper reports a possibility of biaxiality in the nematic liquid crystal formed from aromatic polyesters, BC-n, which are composed of 1,4-dialkyl ester of pyromellitic acid and 4,4'-biphenol. In these BC-n polyesters, as a general trend, the microsegregation of aromatic backbone and flexible side chains takes place and the nematic liquid crystal appears after these layered phases melt. X-Ray diffraction pattern from oriented nematic fiber shows unusual inner reflection with a large spacing around 20 angstrom in addition to normal outer reflection with a spacing of 4.5 angstrom on equatorial line, indicating that there are two types of packing correlation in a direction perpendicular to the director, n, in other words, there is a biaxiality. Optical microscopic textures exhibit exclusively the two-brush disclinations with vertical bar s vertical bar = 1/2, which also conforms to the biaxial nematic order. The spacing of inner equatorial reflection approximates to the layer spacing in the layered mesophase formed from the same homologues. This strongly suggests that the layered aggregation is still remained in the nematic liquid crystals, and its board-like shape is responsible for the biaxiality.