含雙苯基乙炔及三苯基雙乙炔之高雙折射率液晶與可光聚之液晶單體的合成與應用

Abstract

本論文主要分為三個部份，第一部份是含氟與異硫氰基聯苯基取代之雙苯基乙炔之合成與熱性質之研究，第二部份是含異硫氰基取代之超高雙折射率三苯基雙乙炔之合成與熱性質之研究，第三部份為反應型液晶單體於垂直配向模式之液晶元件之光電性質與型態學研究。 本研究第一部份是合成出兩系列之液晶化合物，第一系列化合物為末端不同烷基取代的聯苯基以三鍵連接末端含有氟原子的苯環所形成的雙苯基乙炔液晶化合物。本系列化合物的熔點在82.5 ~ 200 oC之間，澄清點在136.2 ~ 212.9.7 oC 之間，液晶相範圍在5.5 ~ 81.6度，所有化合物皆具有向列型液晶相。第二系列化合物為末端不同烷基取代的聯苯基以三鍵連接末端含有異硫氰基的苯環所形成的雙苯基乙炔液晶化合物。本系列化合物的熔點在84.8 ~ 185.7 oC之間，澄清點在 188.1 ~ 266 oC之間，液晶相範圍在49.4 ~ 124.9度，所有化合物皆具有向列型液晶相。所有的化合物具有高雙折射率，□n從0.36到0.49不等。 本研究第二部份是合成出四系列之液晶化合物，第一系列化合物為三苯基雙乙炔之液晶化合物，在兩端分別導入戊基及異硫氰基，中間苯環導入側向甲基，末端苯環側面導入無取代基及氟原子，熔點在103.1 oC ~ 103.5 oC之間，澄清點在188.3 oC ~ 225 oC之間，液晶相範圍達84.8 oC ~ 122度 。第二系列化合物為三苯基雙乙炔之液晶化合物，在兩端分別導入戊烷氧基及異硫氰基，中間苯環導入側向氟基，末端苯環側面導入無取代基及氟原子。熔點在96.0 oC ~ 150.9 oC之間，澄清點在231.6 oC ~ 259.2 oC之間，液晶相範圍達56.7 oC ~ 132.6度。第三系列化合物則是將苯環用聯苯環取代之，中間苯環導入側向乙基，而末端苯環上仍是異硫氰基，末端苯環側面導入包括甲基、乙基、氟原子及無取代基。本系列化合物的熔點在44 oC ~115.9 oC之間，澄清點在225.6 oC ~ 241.4 oC之間，液晶相範圍非常寬廣，約在126.2 oC ~ 145.3度。第四系列化合物則是將苯環用萘環取代之，中間苯環導入側向乙基，而末端苯環上仍是異硫氰基，末端苯環側面導入無取代基及氟原子。本系列化合物的熔點在119.9 oC ~ 157 oC之間，澄清點在187.2 oC ~ 283.6 oC之間，液晶相範圍約為67.3 oC ~ 141.6度。所有的化合物具有高雙折射率，□n從0.50到0.73不等，皆為文獻上少見之超高雙折射率液晶化合物。 本研究第一部份與第二所部份所合成之部分液晶化合物具有接近室溫之熔點、低融解熱焓值、寬廣的液晶相範圍及超高雙折射率，有潛力應用於調配液晶共融物，或應用在PDLC，反射式液晶顯示器及紅外線調節器上。 本研究第三部份是合成出兩系列之反應型液晶單體，於聯苯基的側面導入包括氟原子、單甲基及雙甲基，並用已知的聯苯與萘環之反應型單體混合適當比例的之負型液晶及光起始劑，經UV光照射後產生垂直配向膜而製作成垂直配向模式之液晶元件。在此模式下 (VA mode) 下，探討其穿透度、對比度及反應時間等光電特性。結果發現，VA LC cell的反應時間與垂直配向膜表面粗糙度的大小是成正比的。若垂直配向膜表面型態越平整分佈，則對比度越好，如M4與M5。由於結構本身不含烷鏈，因此所有垂直配向膜的表面型態皆是水滴或米粒狀。

Sythesis and mesomorphic properties of fluoro and isothiocyanato biphenyl tolane and isothiocyanato bistolane liquid crystals were described in the first and second parts of this study. In the third part of this study, we aim to synthesize reactive liquid crystal monomers used for photo vertical process for VA mode LCD. In the first part of this thesis, two series of liquid crystals were synthesized and characterized. In the first series of compounds, their melting points are in the temperature range from 82.5 ~ 200 oC, and their cleaning points are in the temperature range from 136.2 ~ 212.9.7 oC. Their mesomorphic ranges cover from 5.5 ~ 81.6 degrees. All these compounds exhibit nematic phase. In the second series of compounds, their melting points are in the temperature range from 84.8 ~ 185.7 oC, and their cleaning points are in the temperature range from 188.1 ~ 266 oC. Their mesomorphic ranges cover from 49.4 ~ 124.9 degrees. All these compounds exhibit nematic phase. Two series of liquid crystals exhibt high birefringence from 0.36 to 0.49. In the second part of this thesis, four series of liquid crystals were synthesized and characterized. The goal of this study is aimed to synthesize four series of highly conjugated bistolane liquid crystals. The first series of liquid crystals containing a lateral methyl substituent on the middle phenyl ring and an pentyl and isothiocyanato groups on both ends. The synthesized liquid crystals exhibit melting points ranging from 103.1 oC ~ 103.5 oC, and their cleaning points are in the temperature range from 188.3 oC ~ 225 oC. Their mesomorphic ranges cover from 84.8 ~ 122 degrees. The second series of liquid crystals containing a lateral fluoro substituent on the middle phenyl ring and an pentyloxy and isothiocyanato groups on both ends. The synthesized liquid crystals exhibit melting points ranging from 96.0 oC ~ 150.9 oC, and their cleaning points are in the temperature range from 231.6 oC ~ 259.2 oC. Their mesomorphic ranges cover from 56.7 ~ 132.6 degrees. The third series of liquid crystals containing a biphenyl and a lateral ethyl substituent on the middle phenyl ring, and different lateral groups were introduced on the right-hand side containing an isothiocyanato phenyl ring. Their melting points are in the temperature range from 44 oC ~115.9 oC, and their cleaning temperature are in the temperature range from 225.6 oC ~ 241.4 oC. This series compounds have widest nematic temperature ranges, and the ranges are from 126.2 ~ 145.3 degrees. The fourth series of liquid crystals containing the same terminal isothiocyanato group on the right-hand side phenyl ring and alkoxy chains of varying length on the naphthyl ring. Their melting points are in the temperature range from 119.9 oC ~ 157 oC, and their cleaning temperature are in the temperature range from 187.2 oC ~ 283.6 oC. Their mesomorphic ranges cover from 67.3 ~ 141.6 degrees. Some of the synthesized of liquid crystals in the first and second part of this thesis exhibit lower melting points around room temperature, small heat fusion enthalpy, wide nematic range and relative super high birefringence. They are suitable for formulating eutectic mixture and for application in PDLC, reflective liquid crystal display, and IR modulator. Finally, in the third part of this study, two series of reactive liquid crystalline monomers which contain different lateral groups were synthesized and characterized. In a test cell, the proper ratio of negative liquid crystal, methacrylate monomer and photoinitiator mixtures were used. After UV exposure, polymer network was formed on the upper and lower layers of VA LCD cell due to phase separation. The electro-optical properties, such as transmittance, contrast ratio and response time of the VA LC cell were studied. The results demonstrate that the response time will increase with increasing the surface roughness of the VA LC cell. Generally, the more uniform morphology has the higher contrast ratio, so M4 and M5 have better contrast ratio of 935 and 950, respectively. Consequently, we confirm that the beadlike morphology of all composite films was observed as shown in the reported literature. This is because that the beadlike morphology was obtained from monomers without spacers, resulted in rigid hard, so not formed filberlike morphology.