低熔点高Δn值双环向列相液晶的合成研究

为了获得低熔点、折射率各向异性(Δn)大的快速响应向列相液晶材料,高Δn值的液晶混合体系中需要加入熔点在50℃以下、Δn大于0.35的双环类液晶组分,以使快速响应向列相液晶材料满足室温工作的要求。本文合成了异硫氰基含氟二苯乙炔类液晶化合物;一方面由于在分子苯环侧位引入F原子,减小分子间作用力,使化合物的熔点下降;另一方面在两个苯环间引入三键、分子末端接入异硫氰基极性基团,增加了分子的共轭性,提高了目标化合物的Δn值。获得了熔点分别为31℃和50℃、Δn为0.39和0.40,这两种低熔点化合物与目前已具有的毫秒级快速响应向列相液晶化合物混合,可使其熔点低至10℃以下。

Synthesis of two-ring nematic phase liquid crystal compounds with low melting point and high Δn value

In order to develop liquid crystal materials with low melting point, high birefringence (Δn) and fast response, we need to join in double ring type LC compounds with the low melting point under 50℃ and the Δn value with more than 0.35 in high Δn values of the liquid crystal mixture system, which can make fast response nematic phase liquid crystal materials meet the requirements of working at room temperature. The liquid crystal compounds of isothiocyanate diphenylacetylene were designed and synthesized in this paper. By adding the isothiocyanate group at the molecular terminal, the birefringence of the liquid crystal increased. At the same time, F atom is introduced at the benzene ring side to reduce the viscosity of the liquid crystals. The results showed that the two target compounds' Δn value were 0.39 and 0.4, and the melting points were 31℃ and 50℃, respectively, which would decrease the melting point of the present liquid crystals with a few milliseconds in response time as low as 10℃.