ABSTRACT

In this paper, we discuss the effect of different terminal polar groups attached to biphenyl units of 2,3,4-trihydroxy benzonitrile-based trimers on the mesomorphic properties. The thermal properties of two new series namely 2,3,4-tris-[ω-(4-fluorobiphenyl-4’-yloxy)alk-1-yloxy]benzonitrile and 2,3,4-tris-[ω-(biphenyl-4’-yloxy)alk-1-yloxy]benzonitrile were compared with cyano-substituted analogous which was previously reported. Two new trimers, which are fluoro- and hydrogen-substituted compounds were synthesised by etherification of 4-fluoro-4’-(n-bromoalkane-1-yloxy)biphenyl or 4-(n-bromoalkane-1-yloxy)biphenyl with 2,3,4-trihydroxy benzonitrile under basic conditions. Polarising optical microscope and differential scanning calorimeter were used for the characterisation of mesogenic properties. The small- and wide-angle X-ray scattering (SAXS and WAXS) measurements show the formation of intercalated trimers in the nematic (N) phase. This study enables to understand the influence of terminal polar groups on the liquid crystalline behaviour of trimers in a non-conventional molecular design.

摘要

在本文中，我们讨论了2,3,4-三羟基苯甲腈基三聚体联苯单元上连接的不同末端极性基团对介晶性质的影响。两个新系列2,3,4-三-[ω-(4-氟联苯-4'-基氧基)烷-1-基氧基]苯甲腈和2,3,4-三-[ω-(联苯)的热性能将-4'-基氧基)烷-1-基氧基]苯甲腈与先前报道的氰基取代的类似物进行比较。通过4-氟-4'-( n-溴烷-1-基氧基)联苯或4-( n-溴烷-1-基氧基)联苯与2,3,4-三羟基苯甲腈在碱性条件下反应。使用偏光光学显微镜和差示扫描量热仪来表征介晶性质。小角和广角 X 射线散射（SAXS 和 WAXS）测量显示向列 (N) 相中插入三聚体的形成。这项研究能够了解末端极性基团对非常规分子设计中三聚体液晶行为的影响。