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Understanding of Molecular Packing in Thermotropic Cubic Phase and Control of the Formation

热致立方相分子堆积的认识及其形成控制

基本信息

批准号：
14550846
负责人：
KUTSUMIZU Shoichi
金额：
$ 2.11万
依托单位：
Gifu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14550846/
关键词：
Liquid Crystal Cubic Mesophase Smectic C Phase Electric Field Effect Viscoelasticity 電場効果粘弾挙動

项目摘要

The aim of this research project is, first, to understand the molecular packing structure in the thermotropic cubic (Cub) mesophase and, second, to elucidate the phase transition mechanism from a lamellar smectic C (SmC) to Cub phase, and, third, to control the formation of the Cub phase. We focused attention to two homologues, 4'-n-alkoxy-3'-nitrobiphenyl-4-carboxylic acids (ANBC) and 1,2-bis(4'-n-alkoxybenzoyl)hydrazines (BASH). In the two homologous series, the basic units constructing the SmC and Cub phases have a common structure, consisting of an aromatic core moiety with a hydrogen-bonding part at the center and an alkyl tail at each end. The following insights were obtained :For the two homologous series, the phase diagrams as functions of temperature, pressure, and alkyl chain length have been established. The ANBC series shows two types of Cub phases, Ia3d-type and Im3m-type, above the temperature region of the SmC phase. The molecular packing models of both Cub phases were proposed. The BASH series shows also SmC and Cub phases, but the SmC phase are formed only when the number of carbon atoms in the alkoxy chain (n) is 8, 9, or 10. The phase type of the Cub phase belongs to Ia3d for n=7-12. Comparing between the phase behaviors of the two series, the roles of the alkyl tail and central hydrogen-bonding part for the Cub phase formation have been revealed. That is, a key origin for the Cub phase formation is temperature-induced packing frustration within SmC layers due to unsymmetrical shape at the interface between the alkyl tail vs aromatic core parts, just like apolar vs. polar competition in lyotropic systems, and therefore, the quasi-binary picture is quite effective for understanding the whole behaviors. In the thermotropic systems, however, the presence of other contributions of intermolecular interactions such as hydrogen-bonding, dipole-dipole interactions etc. is also important and modifies the phase formation.

本研究的目的是，首先了解热致立方相(Cub)中间相的分子堆积结构，其次阐明从片状近晶C(SMC)到Cub相的相变机制，第三，控制Cub相的形成。我们重点研究了两个同系物，4‘-正-烷氧基-3’-硝基-4-联苯-4-羧酸(ANBC)和1，2-双(4‘-正-烷氧基苯甲酰基)肼(BASH)。在两个同源系列中，构成SMC和CuB相的基本单元具有共同的结构，由中心带有氢键部分的芳香族核心部分和两端都有烷基尾部的部分组成。得到以下结论：对于两个同系物，建立了随温度、压力和烷基链长变化的相图。ANBC系列在SMC相的温度区域上方显示了两种类型的Cub相，Ia3d型和Im3m型。提出了两种CuB相的分子堆积模型。Bash系列还显示了SMC和Cub相，但只有当烷氧链上的碳原子数(N)为8、9或10时才形成SMC相。当n=7-12时，Cub相的相类型属于Ia3d。通过对这两个系列相行为的比较，揭示了烷基尾部和中心氢键部分对CuB相形成的作用。也就是说，形成Cub相的一个关键原因是SMC层内的温度诱导堆积受挫，这是由于烷基尾部和芳香族核心部分之间的界面形状不对称造成的，就像溶致体系中的非极性竞争和极性竞争一样，因此，准二元图对于理解整个行为是非常有效的。然而，在热致体系中，分子间相互作用的其他贡献，如氢键、偶极-偶极相互作用等的存在也是重要的，并改变了相的形成。