A series of trimesic acid-based star mesogens containing an octamethylenoxy spacer and two-ring containing side arms with terminal alkoxy groups were synthesised by a divergent approach. A structurally similar mesogen containing a three-ring side arm was also synthesised. All the mesogens and intermediates were characterised thoroughly using FT-IR, 1H NMR, 13C NMR spectroscopy, and elemental analysis techniques. The mesophase characteristics were identified by hot stage optical polarising microscopy (HOPM) and differential scanning calorimetry (DSC), while X-ray was used to confirm the existence of a smectic A (SA) phase. The HOPM and DSC results revealed the presence of rich polymesomorphism in the star mesogens. The dominance of a SA phase in the series is attributed to the steric repulsion associated with steric asymmetry. The change of the side arm from two rings to three rings was found to increase the mesophase stability.
我们采用发散方法合成了一系列基于三肟酸的星形中间体,这些中间体含有八亚甲基烯氧基间隔物和带有末端烷氧基的双环侧臂。此外,还合成了一种结构类似的含有三环侧臂的中间体。利用傅立叶变换红外光谱、1H NMR、13C NMR 光谱和元素分析技术对所有中间体和中间产物进行了全面的表征。热台光学偏振显微镜(HOPM)和差示扫描量热仪(DSC)确定了中间相的特征,而 X 射线则用来确认是否存在共晶 A(SA)相。HOPM 和 DSC 结果表明,星形介质中存在丰富的多介质形态。SA 相在该系列中占主导地位的原因是与立体不对称相关的立体斥力。将侧臂从两个环变为三个环可以提高介相的稳定性。