【摘要】 以2-溴-5-吡啶甲醛和5-溴-2-吡啶甲醛为起始原料,合成出4种新型含吡啶环二联芳基和三联芳基化合物,总收率20%~30%。热性能研究结果表明,二联芳基化合物未呈现出液晶相,而三联芳基化合物在加热和冷却过程中均表现向列相液晶态,且当氮原子位于正丁基的间位时,其与不含氮原子的三联苯化合物(2c)相比,熔点降低了11.7℃,清亮点升高6.3℃,液晶相区拓宽了18℃,表现出了良好的热性能。光电性能测试结果表明,用吡啶环替代苯环后,化合物的光学各向异性值均较参比化合物(1c或2c)增大;当N原子位于正丁基的邻位的化合物,介电各向异性值较参比化合物增大,且液晶的阈值电压、饱和电压均降低。通过对三环同分异构体化合物的不同构象能量态的计算分析,解释了介电各向异性的变化规律。更多还原

【Abstract】 Four new bi-aryl and tri-aryl compounds containing pyridine ring were synthesized by using2-bromopyridine-5-carbaldehyde and 5-bromopyridine-2-carbaldehyde as starting materials. The total yields are around 20% ~ 30%. Thermal analysis results show that the bi-aryl compounds exhibit no mesophase,while the tri-aryl compounds exhibit nematic phase during both heating and cooling process. For the compound with nitrogen atoms located at the ortho position of n-butyl group,its melting point is decreased by 11. 7 ℃and its clearing point is increased by 6. 3 ℃,and the mesophase range is broadened by 18 ℃,compared with the reference terphenyl compound( 2c). Optic-electronic property analysis results show that the birefringence is improved when one of benzene ring in the reference compounds( 1c or 2c) is replaced by with pyridine ring.Besides,the dielectric anisotropy values are increased when the nitrogen atoms locate at ortho position of nbutyl,and the threshold voltage and saturation voltage are decreased. The rule of the dielectric anisotropy variation is explained by conformation energy calculation of three-ring isomers.更多还原