A series of V-shaped, shape-persistent thiadiazole nematogens, based on an oligo(phenylene ethynylene) scaffold with ester groups connected via alkyloxy spacers, was efficiently prepared by a two-step procedure. Phase engineering results in an optimum of the mesophase range and low melting temperature when the nematogens are desymmetrised with a butoxy and a heptyloxy spacer. The mesophases are enantiotropic and over the whole temperature range nematic. For the optimised mesogen structure, optical investigations by conoscopy monitored a uniaxial nematic phase upon cooling from the isotropic phase to room temperature (ΔT = 150 °C). X-ray studies on magnetic-field-aligned samples of this mesogen family revealed a general pattern, indicating the alignment of two molecular axes along individual directors in the magnetic field. These observations may be rationalised with larger assemblies of V-shaped molecules isotropically distributed around the direction of the magnetic field.
 
                                    一系列基于寡聚
苯乙炔支架的具有酯基和烷氧基间隔连接的V形持形噁二唑向列体,通过两步法高效制备。相位工程导致当向列体通过丁氧和庚氧间隔去对称化时,具有最佳的液晶相范围和低熔点。液晶相具有对掌异构性,整个温度范围内都是向列相。对于优化的液晶相结构,通过共聚显微镜对光学性质进行研究,结果显示在从等向相冷却到室温(ΔT=150℃)时,呈现出单轴向列相。对于该向列体家族的磁场排列样品进行的X射线研究揭示了一般的模式,表明两个分子轴沿着磁场中的单个方向排列。这些观察结果可以通过大型V形分子的组装来解释,这些分子在磁场方向周围具有等向分布。