ABSTRACT Heterocyclic mesogenic compounds are one of the interesting liquid crystals. Here, a series of 1-methyl-1H- benzimidazole-based mesogenic compounds incorporating ethynyl moiety, 2-[4-[2-[4-(alkoxy)phenyl]ethynyl]phenyl]-1-methyl-1H-1,3-benzimidazole derivatives (nPEPMx) with terminal groups of H, CH3 and NO2 (coded as nPEPMH, nPEPMM and nPEPMN, respectively), are synthesised and their properties are evaluated. It is noted that the compounds nPEPMx with short alkoxy chain less than 9 carbon atoms display enantiotropic nematic mesophases, whereas corresponding reference compounds without ethynyl moiety have enantiotropic smectic mesophases. The mesophase ranges of compounds nPEPMx 50–70°C and 55–108°C on heating and cooling for nPEPMH, 76–106°C and 98–142°C for nPEPMM, and 78–132°C and 130–166°C for nPEPMN, respectively. Besides, compounds nPEPMx show obviously large birefringence of 0.501–0.641, suggesting a potential application in liquid crystal mixture. The high birefringence may result from its large π-conjugated molecule structure incorporating ethynyl and benzimidazole π-conjugated mesogenic unit. GRAPHICAL ABSTRACT

中文翻译：

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含乙炔基部分的1-甲基-1H-苯并咪唑基介晶化合物的制备及性质

摘要杂环介晶化合物是一种有趣的液晶。在这里，一系列包含乙炔基部分的 1-甲基-1H-苯并咪唑基介晶化合物，2-[4-[2-[4-(烷氧基)苯基]乙炔基]苯基]-1-甲基-1H-1,3合成了末端基团为 H、CH3 和 NO2（分别编码为 nPEPMH、nPEPMM 和 nPEPMN）的苯并咪唑衍生物 (nPEPMx) 并评估了它们的性质。值得注意的是，具有少于 9 个碳原子的短烷氧基链的化合物 nPEPMx 显示出对映向列中间相，而没有乙炔基部分的相应参考化合物具有对映性近晶中间相。化合物的中间相范围 nPEPMx 加热和冷却时 nPEPMx 为 50-70°C 和 55-108°C，nPEPMM 为 76-106°C 和 98-142°C，以及 78-132°C 和 130-166°C分别为 nPEPMN。除了，化合物 nPEPMx 显示出明显的大双折射 0.501-0.641，表明在液晶混合物中的潜在应用。高双折射可能是由于其包含乙炔基和苯并咪唑 π 共轭介晶单元的大 π 共轭分子结构所致。图形概要