Two novel series of unsymmetrically substituted 1,2,4-oxadiazole viz., R.Ox.C*Cn compounds are synthesized and characterized. An optically active, (S)-(+)-methyl 3-hydroxy-2-methylpropionate is used to introduce a chiral center in the molecule. A biphenyl moiety prepared by Suzuki coupling reaction is directly attached to the oxadiazole core at C-5 position. Investigations for the phase behavior revealed that the series with a benzyl group on one end of the oxadiazole core exhibits an 1D orthogonal smectic-A phase while the second series with dodecyl flexible end chain shows orthogonal smectic-A and tilted chiral smectic-C (SmC*) phases over a wide range of temperatures. The smectic-C phase exhibits ferroelectric (FE) polarization switching. The mesomorphic thermal stabilities of these compounds are discussed in the domain of the symmetry and the flexibility of the alkyloxy end chain length attached to the chiral center.
两个新颖的不对称取代的1,2,4-噁二唑系列,即R.Ox.C*Cn化合物已合成并表征。使用光学活性的(
S)-(+)-甲基3-羟基-2-甲基
丙酸酯在分子中引入手性中心。通过Suzuki偶联反应制备的
联苯基团直接连接到噁二唑核心的C-5位置。对相行为的调查显示,具有苄基团在噁二唑核心一端的系列表现出1D正交液晶-A相,而具有
十二烷基柔性端链的第二个系列在广泛的温度范围内展现出正交液晶-A和倾斜手性液晶-C (SmC*)相。液晶-C相展示了
铁电(FE)极化开关。讨论了这些化合物的液晶热稳定性在与连接到手性中心的烷氧基端链长度的对称性和柔韧性领域内。