摘要
为了研究液晶材料结构与性能的关系,本文以含乙炔桥键的四环异硫氰酸酯化合物为研究对象,芳基硼酸和3-氟-4-溴碘苯为起始原料,经6步反应合成了12种目标化合物,LC纯度大于99%,采用核磁共振、红外光谱对其结构进行了表征。采用DSC和POM对目标化合物的介晶性进行了研究,采用外推法对其双折射率和介电各向异性值进行了测试。结果表明:目标化合物具有300℃以上高清亮点、150℃以上向列相温度区间、0.40~0.51的双折射率以及大于17的介电各向异性值。对于同一系列化合物,随着末端烷基链的增长,化合物熔点降低,但呈现近晶相的趋势增加。在Y、Z位引入侧向氟取代基,熔点和清亮点均降低;X位再引入侧向氟取代基,熔点上升、清亮点下降。用环己烷替代左边第一个苯环,化合物熔点降低、向列相温度区间变宽。引入侧向氟取代基使双折射率下降0.008~0.036。目标化合物有利于提高混合液晶配方的双折射率、清亮点和降低阈值电压。
In order to investigate the relationship between the structures and properties of LCs, twelveisothiocyanate liquid crystals composed of four-ring core and ethynyl bridge were synthesized via six steps based on arylboronic acid and 1-bromo-2-fluoro-4-iodobenzene. Their structures were confirmed by infrared spectrometry （IR） and 1H-nuclear magnetic resonance （1 H NMR）. The mesomorphic properties, birefringence and dielectric anisotropy of these compounds were investigated. The result reveals that all these compounds exhibit high clearing points （〉300 ℃）, wide nematic phase range （〉150 ℃）, high birefringence （An =0.40-0.51） and large dielectric anisotropy （A〉17）. The melt- ing points of these compounds decreased with increasing the carbon number of alkyl chain, while the smectie phase intervals enlarged. Lateral fluorines in the position of Y, Z result in a drop of the melt- ing points and the clearing points, but an additional fluorine in the position of X results in an increase of the melting points and decrease of the clearing points. Replacement of the left benzene ring by cy- clohexane is useful to lower the melting point and increase nematic phase range. The introduction of lateral fluorine will reduce the birefringence of 0.008-0.036. The target compounds are useful for ele- vating the birefringence values, clearing points and reduce the threshold voltage of liquid crystal mix- tures.
出处
《液晶与显示》
CAS
CSCD
北大核心
2017年第9期692-700,共9页
Chinese Journal of Liquid Crystals and Displays
基金
国防基础科研项目(No.B0520132007
No.B1120132028)
陕西省科技攻关项目(No.2016GY-212)
应用光学国家重点实验室开放基金(No.Y6133FQ112)
国家自然科学基金(No.61378075)~~
关键词
液晶
乙炔
异硫氰酸酯
介晶性
双折射率
liquid crystals
ethynyl
isothiocyanate
nematic phase
birefringence
