Molecular theory of dendritic liquid crystals: self-organisation and phase transitions
Molecular theory of dendritic liquid crystals: self-organisation and phase transitions
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树枝状液晶的分子理论：自组织和相变
DOI：
10.1039/b416710d
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发表时间：
2005
影响因子：
--
通讯作者：
D. Photinos
中科院分区：
文献类型：
--
作者：
A. G. Vanakaras;D. Photinos
我们基于明确定义的近似和这些大而复杂的超分子实体自组织的主要相互作用，提出了液晶树枝状大分子的易于处理的分子理论描述。我们建立了树枝状大分子的构型配分函数，显式地考虑了它们的构象和链段相互作用。提出了两种近似方案：第一种方案基于树枝状大分子作为一个整体的有效相互作用，第二种方案基于树枝状大分子中包含的介晶单元之间的相互作用。给出了第一种方案下相变的晶格计算结果，它们表明，最小限度地包含形状各向异性和亚分子分配到化学上不同的部分足以重现实验观察到的各种相和相序列，并提供了对这些相变的构象方面的见解。在第二种方案中，对树枝介晶系统的描述简化为介晶二聚体的系综。该方案可以容易地扩展到描述液晶低聚物和由各种结构中的柔性间隔物连接的介晶单元组成的聚合物。因此，它为处理超分子和大分子体系的介晶相变提供了一种统一的方法，这些体系可以通过以不同的拓扑方式连接相同的亚分子单元来构建。
We present tractable molecular theory descriptions of liquid crystalline dendrimers based on clearly defined approximations and in terms of the dominant interactions underlying the self-organisation of these large and complex supermolecular entities. We formulate the configurational partition function for dendrimers, taking explicit account of their conformations and segmental interactions. Two approximate schemes are presented: the first is based on the effective interactions of the dendrimers as a whole while the second scheme is based on the interactions among the mesogenic units contained in the dendrimers. Results of lattice calculations for phase transitions in the context of the first scheme are presented and they show that the minimal inclusion of shape anisotropy and of sub-molecular partitioning into chemically distinct parts is sufficient to reproduce the variety of phases and phase sequences observed experimentally and provides insights into the conformational aspect of these transitions. In the second scheme, the description of the dendromesogenic system reduces to that of an ensemble of mesogenic dimers. This scheme can be readily extended to the description liquid crystalline oligomers and polymers consisting of mesogenic units connected by flexible spacers in various architectures. It thus provides a unified approach for treating mesomorphic phase transitions of supermolecular and macromolecular systems that can be built by connecting the same submolecular units in topologically different ways.