臺灣博碩士論文加值系統

本次研究以雙苯并吡啶與苯并吡啶為中心核，並含8個側鏈基團，側鏈基團為n個柔軟間距的氧烷基，BQ8-n (2,3,2’,3’-四[3,4-雙氧烷基-苯基]-[6,6']雙苯并吡啶與Q8-n (2,3,7,8-四-[3,4-雙氧烷基-苯基]-毗井[2,3g]苯并吡啶這二系列均有碟狀液晶相。先合成其中間產物1,2-雙-(3,4-雙氧烷基-苯基)-(乙烷)-1,2-雙酮，在醋酸溶液中與3,3'-雙胺基聯苯胺及1,2,4,5-(四氯胺基偶氮苯)反應分別得到BQ8-n與Q8-n二種化合物，我們利用微差熱掃描卡計與偏光顯微鏡觀察其相轉移溫度及晶相變化與柔軟間距(n)的關係。發現上述二系列(含八個側鏈基團)在特定溫度範圍有碟狀液晶晶相，但是只有四個側鏈基團的分子卻沒有。
在Q8-n (n=5~12)系列中，發現溶化溫度(Tc)及溶化螪(ΔSc)會隨柔軟間距(n)變化，呈現出明顯的奇偶效應，在等方性溫度(Ti)及等方性螪(ΔSi)上也發生此效應。又發現液晶相生成範圍會隨柔軟間距(n)增加而縮小，至n>10為止。此二系列的分子量鑑定均使用飛行質譜儀。
以苯并吡啶為中心核含8個側鏈基團，其中6個位置以八碳氧烷取代，另外2個位置以羥基取代，形成不對稱碟狀分子單體，此單體是MQ8-a與MQ8-b二種異構物的混合，需以離心薄層分析儀分離純化，再進行聚合反應得PQ8-a與PQ8-b，這二種聚合物具有碟狀液晶相。

Abstract
Two series of disc-like molecules (schemeⅠ5 and schemeⅡ5) with a quinoxaline or a biquinoxaline hetrocyclic core and eight n-alkoxy side chains which exhibits a discotic mesophase, viz., Q8-n and BQ8-n (2,3,7,8-Tetra-[3,4-dialkoxyphenyl]-pyrazino-[2,3-g] quinoxaline and 2,3,2',3'-Tetra-[dialkoxyphenyl]-[ 6,6'] biquinoxaline, respectively] were synthesized. The homologous series of disc-like molecules, (schemeⅠ5 and schemeⅡ5) are easily accessible by condensation of1,2-Bis-(3,4-dialkoxy-phenyl)-ethane-1,2-dione with biphenyl-3,4,3',4'-tetraamine and benzene-1,2,4,5-tetraamine respectively, in the presence of acetic acid. The phase transition temperatures were determined by DSC and POM. The dependence of side chains density has also been observed. The disc-like molecules (schemeⅠ5 and schemeⅡ5) with eight alkoxy side chains exhibited discotic liquid crystalline behavior, whereas they were not liquid crystalline with four side chains. In the series of Q8-n (n=5~12) an odd-even fluctuation with n in the flexible part of the molecular skelton affects both melting temperatures and molar melting entropies, similar effect is also observed for isotropization temperatures and isotropization entropies. The mesophase range in this series appears to increase at first with n and then decreases after attaining a maximum value for Q8-10 (n=10). To evaluate the exact mass of the compounds, matrix—assited laser desorption time-of-flight mass spectroscopy (MALDI-TOF MS) was applied.
The combination of the condensation reactions with a selective cleavage of methoxy group next to octoxy groups (n=8) extends the versatility of the procedure and provides additional possibilities of the synthesis of unsymmetrically substituted discotics. In this report, the synthesis of dihydroxyhexaoctoxy side chains in the series of MQ8-a and MQ8-b 11 as shown in schemeⅤis of special interest, since it represents a central precursor molecule for difunctional discotic monomers. Selective cleavage of the methoxy group of 1-(3,4-bis-octyloxy-phenyl)-2 -(3-methoxy -4-octyloxy-phenyl)-ethane-1,2-dione 9 with 48% HBr in refluxing acetic acid led to 10, following condensation with benzene-1,2,4,5-tetraamine and purification by column chromatography affords two monomers 11. Subsequent polycondensation reaction in solution with various alkane-α, ω-dioic acid dichloride led to new polyesters, PQ8-a and PQ8-b with disc-shaped quinoxaline mesogenic groups in the main-chain, respectively. Both polymers PQ8-a and PQ8-b show discotic mesophase.

目錄
中文摘要
英文摘要
致謝
目錄
List of Scheme
List of Figure
List of Table
第一章 緒論
1-1 前言
1-2 碟狀液晶簡介
1-3 碟狀液晶分類
1-4 液晶化合物的化學構成及其性質
1-5 液晶聚合物之簡介
1-6 液晶相之鑑定
1-7 研究動機
第二章 實驗
2-1 藥品
2-2 實驗儀器與測試方法
2-3 合成方法
第三章 單體之合成與鑑定
3-1 以Biquinoxalines 為中心接八個柔軟側鏈基團之單體合成與鑑定
3-2 以Quinoxalines 為中心接八個柔軟側鏈基團之單體合成與鑑定
3-3 含Quinoxalines 之聚酯主鏈型液晶高分子單體合成與鑑定
3-4 含Quinoxalines 之聚酯主鏈型液晶高分子合成與鑑定
第四章 結果與討論
4-1 液晶相之鑑定與其物性之探討
4-2 光學性質之探討
第五章 討論
第六章 總結

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