含4-[1-(4-烷基苯基)-乙炔基]4’-氟基-α-甲基菧液晶化合物之合成研究

Abstract

本研究主要合成出以4-[1-(4-烷基苯基)-乙炔基]4’-氟基-α-甲基菧為主幹的三系列液晶化合物。三系列化合物皆呈現向列型液晶相。第一系列化合物的熔點在126.3∼165.8 ℃之間，澄清點在193.6∼215 ℃之間，液晶相範圍寬廣，可達49.2∼72.5 ℃。第二系列化合物在中間苯環5-位置導入甲基側取代基，其熔點在56.1∼90.4 ℃之間，澄清點在151.7∼183.2℃之間，澄清點與熔點對第一系列而言均下降；液晶相溫度範圍在三系列中最為寬廣，可達92.8∼109.8 ℃。第三系列化合物在中間苯環2-位置導入甲基側取代基，其熔點在55∼86.9 ℃之間，澄清點在115.1∼151.8 ℃之間，液晶相範圍寬廣，可達52.3∼73.3 ℃；澄清點與熔點對第一系列而言均下降，澄清點呈現出明顯的奇偶效應。

Three series of new liquid crystals, i.e., 4-[1-(4-alkylphenyl)- ethynyl]-4’-fluoro-α-methylstilbenes, 4-[1-(4-alkylphenyl)-ethynyl] -5-methyl-4’-fluoro-α-methylstilbenes, 4-[1-(4-alkylphenyl)-ethynyl]- 2-methyl-4’-fluoro-α-methylstilbenes, were synthesized and characterized. All three series of compounds exhibit a nematic liquid crystal (LC) phase. For the first series of compounds, their melting points are in the temperature range from 126.3 to 165.8℃ and their clearing temperature are in the temperature from 193.6 to 215℃. Their mesomorphic ranges cover from 49.2 to 72.5 degrees. For the second series of compounds which containing a methyl group on the 5 position of the stilbene core, their melting points are in the temperature range from 56.1 to 90.4℃ and their clearing temperature are in the ranges from 151.7 to 183.2℃. Their mesomorphic ranges cover from 92.8 to 109.8 degrees. For the third series of compounds which containing a methyl group on the 2 position of the stilbene core, their melting points are in the temperature range from 55.0 to 86.9℃ and their clearing temperature are in the ranges from 115.1 to 151.8℃. Their mesomorphic ranges cover from 52.3 to 73.3 degrees. Introducing a lateral methyl substitution will decreases dramatically the melting point and clearing temperature. However, the second series of compounds show the widest nematic temperature range.