含有偶氮基团和3-氟-4-氰基苯基的液晶化合物的合成及其性质分析

Synthesis and Properties of Liquid-crystalline Compounds Containing Azobenzene and 3-Fluoro-4-cyanophenyl Groups

以溴代异烷烃和对氨基苯甲酸为起始原料,设计合成了4种同时含偶氮苯基团和3-氟-4-氰基苯基的液晶化合物,并对重氮偶合反应和Williamson醚化反应过程中存在的问题进行了探讨。找出了较为合理的解决方法:延长偶合反应时间至5 h或以上,苯酚相对于重氮盐过量(物质的量之比为2∶1),冷却后酸化醚化产物,酯化反应中采用DCC(N,N-二环己基碳二亚胺)作为脱水剂。在优化后条件下反应,得到了较为满意的结果。同时对4种化合物的液晶相变进行了研究,通过DSC、POM测定,确定这些化合物皆为热致性互变液晶化合物,且都具有较高的清亮点。

Four new compounds with 3-fluoro-4-cyanophenyl and azobenzene groups were synthesized and characterized using bromoisoalkane and p-aminobenzoic acid as raw materials.The problems encountered in coupling and Williamson reactions were investigated.Satisfactory yields were obtained under the conditions of reaction time of coupling 5 h,n（phenol）∶n（diazonium） =2∶1,acidifing the Williamson reaction product after cooling and using N,N-dicyclohexylcarboimide（DCC） as dehydrant in the esterification.The liquid-crystalline behaviors of these compounds were also investigated with differential scanning calorimetry（DSC） and polarizing optical microscopy（POM）.The results showed that all of them were of higher clearing point.