The influence of shape and size of silyl units on the properties of bent-core liquid crystals—from dimers via oligomers and dendrimers to polymers
The influence of shape and size of silyl units on the properties of bent-core liquid crystals—from dimers via oligomers and dendrimers to polymers
复制标题
甲硅烷基单元的形状和尺寸对弯核液晶性能的影响——从二聚体到低聚物和树枝状聚合物再到聚合物
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
C. Tschierske
中科院分区：
文献类型：
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作者：
Christina Keith;G. Dantlgraber;R. A. Reddy;U. Baumeister;M. Prehm;H. Hahn;H. Lang;C. Tschierske
合成并研究了一系列结合介晶弯曲核单元和含硅连接单元（硅氧烷和碳硅烷）的低聚和树枝状液晶材料。研究了甲硅烷基单元的尺寸和形状对中间相类型和转换行为的影响。基于线性低聚硅氧烷的二聚体和树枝状碳硅烷显示出铁电和非经典反铁电切换单层近晶相，具有与非手性域共存的暗团聚结构，而环状低聚硅氧烷和倍半硅氧烷衍生物则具有反铁电切换和具有双层结构的双折射近晶相。结论是，铁电性和层畸变需要一定尺寸的甲硅烷基和单层结构，其中每层通过甲硅烷基化单元形成的子层去耦。
A series of oligomeric and dendritic liquid crystalline materials combining mesogenic bent-core units and silicon-containing linking units (siloxanes and carbosilanes) was synthesized and investigated. The influence of the size and shape of the silyl units upon the mesophase type and the switching behaviour was investigated. Linear oligosiloxane based dimers and dendritic carbosilanes show ferroelectric and non-classical antiferroelectric switching monolayer smectic phases with dark conglomerate textures coexisting with achiral domains, whereas cyclic oligosiloxane and silsesquioxane derivatives have antiferroelectric switching and birefringent smectic phases with double layer structure. It is concluded that ferroelectricity and layer distortion require a certain size of the silyl groups and a monolayer structure where each layer is decoupled by sublayers formed by the silylated units.