含亚甲氧基桥键负性单体液晶的制备及性能研究

含亚甲氧基桥键负性单体液晶由于具有较大的负介电各向异性,较低的旋转粘度、良好的相溶性而被广泛应用于VA-TFT配方中,但其合成步骤长,合成及提纯难度大。本文讨论了含亚甲氧基桥键及苯环侧向氟取代的负介电各向异性单体液晶的合成方法,该方法主要采用2,3-二氟-4-乙氧基苯酚与含不同长度烷基链的苯磺酸酯反应引入亚甲氧基桥键,避免了常用醚化方法中卤代物的使用和卤素离子对单体液晶性能的影响。使用1 H NMR对目标单体液晶的结构进行了表征;采用DSC、热台偏光显微镜、LCR测试仪等对目标单体液晶的相变温度、光学各向异性、介电各向异性等一系列液晶性能参数进行了测试。

Preparation and properties of oxymethylene-bridged negative liquid crystal

Oxymethylene-bridged negative liquid crystal has been widely used in VA-TFT mixtures owing to its relatively large negative dielectric anisotropy, low viscosity and good phase solubility with other liquid crystals. However, the long synthetic route and difficulty in purification have been obstacles in application. In this paper, three oxymethylene-bridged negative liquid crystal compounds were synthesized via the etherification reaction of 4-ethoxy-2, 3-difluorophenol with different alkylbenzene sulfonate. The method effectively avoids impurity resulting from the introduction of halogen ions in conventional method. All key compounds were characterized by ¹H NMR spectroscopy. The liquid crystal properties, such as phase transition temperature, optical anisotropy and dielectric anisotropy were measured by DSC, TPOM and LCR testing analyzer.