Influence of the core structure on the development of polar order and superstructural chirality in liquid crystalline phases formed by silylated bent-core molecules: naphthalene derivatives
作者:R. Amaranatha Reddy、U. Baumeister、C. Keith、C. Tschierske
DOI:10.1039/b614089k
日期:——
Bent-core molecules based on a bent 2,7-disubstituted naphthalene unit and heptamethyltrisiloxane units at one or both ends of the aliphatic side chains were synthesized and investigated by polarized light microscopy, differential scanning calorimetry, X-ray scattering and electrooptical investigations. The effect of fluorine substitution at the periphery of the rigid core and of the replacement of ether oxygens by carboxylate groups as linking units between the aromatic core and the flexible terminal chains was also investigated. All compounds form broad regions of liquid crystalline phases. Different types of non-polar and polar, i.e. antiferroelectric and ferroelectric switching smectic phases, and columnar phases were observed, depending on the molecular structure. Most interestingly, a temperature dependent transition from an antiferroelectric switching to a ferroelectric switching oblique columnar phase was observed. All double-silylated compounds show switching by a collective rotation around the molecular long axis, a process which switches the superstructural chirality in these LC systems.
通过偏光显微镜、差示扫描量热仪、X 射线散射和电光研究,合成了基于弯曲的 2,7 二取代萘单元和脂肪族侧链一端或两端的七甲基三硅氧烷单元的弯曲核心分子。此外,还研究了刚性核心外围的氟取代以及芳香核心和柔性侧链之间的连接单元羧酸基取代醚氧的影响。所有化合物都形成了广泛的液晶相区域。根据分子结构的不同,观察到了不同类型的非极性和极性相,即反铁电和铁电转换 smectic 相以及柱状相。最有趣的是,从反铁电转换到铁电转换斜柱状相的转变与温度有关。所有双硅烷化化合物都显示出围绕分子长轴的集体旋转切换,这一过程切换了这些 LC 系统中的超结构手性。