含聯苯基乙炔及萘基乙炔取代之異硫氰基雙苯基乙炔液晶之合成

Abstract

本研究成功的合成三系列末端含有異硫氰基之液晶化合物。所合成之化合物皆具有寬廣的液晶相範圍，且皆為雙向變之向列型液晶。第一系列化合物主結構中含有萘基，合成具有共軛之雙苯環結構，而在中間本環上有一乙基取代基。本系列化合物熔點在119.9℃~157℃之間，澄清點在187.2℃~279.5℃之間。第二系列為第一系列化合物之改良，在末端苯環側面取代基上多增加一個氟原子，結果顯示，此系列化合物之熔點在122.3℃~153.9℃之間，澄清點在237.3~283.6℃之間，液晶相範圍可達115.0℃~133.3℃，整體比第一系列略長。第三系列之化合物，則是以聯苯基取代萘基結構，並在末端導入包括甲基、乙基、氟原子及無取代基等四種化合物；與第一、第二系列比較，第三系列之熔點在78.4℃~115.9℃之間，澄清點在219.9℃~241.2℃之間，結果發現，澄清點的提升，使得整體的液晶相範圍，比同樣碳鏈數的液晶更長，成功的增加液晶相範圍。而三系列化合物皆為高雙折射率液晶化合物，△n從0.5486到0.7301不等，皆為文憲上少見之高雙折射率液晶化合物。

Three series of liquid crystals were synthesized and characterized. All synthesized compounds exhibit mesomorphic properties. The first series liquid crystals, i.e., n-NTP(Et)TP-NCS compounds, their melting points are in the temperature range from 119.9℃ to 157.0℃, and their cleaning temperature are in the temperature range from 187.2℃ to 279.5℃. All these compounds exhibit nematic phase. The second series liquid crystals, i.e., n-NTP(Et)TP-(F)NCS compounds, their melting points are in the temperature range from 122.3℃ to 153.9℃, and their cleaning temperature are in the temperature range from 237.3℃ to 283.6℃. Their nematic temperature ranges cover from 115.0℃ to 133.3℃. The temperature ranges large than the first series liquid crystal could be due to the fluoro substitute on the lateral phenyl ring. The third series liquid crystals i.e., n-BTP(Et)TP-(Xn)NCS compounds, their melting points are in the temperature range from 78.4℃ to 115.9℃, and their cleaning temperature are in the temperature range from 219.9℃ to 241.2℃. Because of the naphthalene were replaced by the biphenyl group, their cleaning points are higher than their corresponding liquid crystals in the second series. For the reason, the third series compounds have widest nematic temperature ranges. The ranges are from 125.0℃ to 141.5℃. All three series of liquid crystals exhibit very high birefringence（△n）from 0.61 to 0.73. The liquid crystals synthesized in this study have potential applications in reflective liquid crystal display.