Structural investigation of carbosilane liquid crystalline dendrimers.
Structural investigation of carbosilane liquid crystalline dendrimers.
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碳硅烷液晶树枝状聚合物的结构研究。
DOI：
10.1021/jp805769w
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
I. Grillo
中科院分区：
文献类型：
--
作者：
R. Richardson;E. Agina;N. Boiko;V. Shibaev;I. Grillo
用X射线和中子散射研究了两个系列的液晶树枝状大分子。低世代（第一到第四代）主要表现出近晶相。第五代显示出形成柱状相的趋势，并观察到两种不同的类型。从近晶到柱状的转变已被解释在树枝状核心和介晶单元之间的距离。随着代数的增加，距离增加，直到它变得大于柔性间隔物的最大长度，导致分子形状的变化和柱状相的形成。虽然材料几乎是单分散的，但每个分子中介晶数量的微小变化引起了一些微妙的结构效应。两种共存的结构已被观察到在大的温度范围内，在一些材料和小角中子散射表明，有一些微相分离，这是一个可逆的温度函数。
X-ray and neutron scattering investigations have been made on two series of liquid crystal dendrimers. The low generations (first to fourth) predominantly show smectic phases. The fifth generation shows a tendency to form columnar phases and two different types have been observed. The transition from smectic to columnar has been explained in terms of the distance between the dendritic core and the mesogenic units. As the generation number is increased, the distance increases until it becomes greater than the maximum length of the flexible spacers causing a change in molecular shape and the formation of columnar phases. Although the materials are nearly monodisperse, the small variation in the number of mesogens per molecule gives rise to some subtle structural effects. Two coexisting structures have been observed over large temperature ranges in some materials and small angle neutron scattering indicates that there is some microphase segregation which is a reversible function of temperature.