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.
我们合成并研究了一系列低聚物和树枝状
液晶材料,这些材料结合了中生弯曲核单元和含
硅连接单元(
硅氧烷和
碳硅烷)。研究了
硅烷单元的大小和形状对介相类型和切换行为的影响。基于低聚
硅氧烷的线性二聚体和树枝状
碳硅烷显示出
铁电性和非典型反
铁电性开关单层平滑相,具有与非手性域共存的暗色团块纹理,而环状低聚
硅氧烷和
硅倍半
氧烷衍
生物则具有反
铁电性开关和双折射平滑相双层结构。结论是
铁电性和层畸变需要一定大小的
硅烷基团和单层结构,其中每一层都由
硅烷化单元形成的子层解耦。