具Quinoxaline結構之新穎盤狀液晶材料

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/60545

Title:	具Quinoxaline結構之新穎盤狀液晶材料
Authors:	黎宇軒;Li,Yu-Shiuan
Contributors:	化學學系
Keywords:	液晶;二聚物;盤狀液晶;liquid crystal;dimer;columnar
Date:	2013-07-24
Issue Date:	2013-08-22 11:40:12 (UTC+8)
Publisher:	國立中央大學
Abstract:	系列一成功合成出一系列以quinoxaline雜環結構為主體之dimer分子，藉由改變中間連接基及外部側鏈基來探討液晶性質的差異。系列化合物會分別利用1H、13C、EA及MS來鑑定其結構與純度。而在液晶行為方面，則是藉由POM、DSC、XRD來加以研究，至於分子在液晶相時的堆疊，會使用理論計算配合XRD數據來做更進一步的探討。此外，關於系列化合物的熱穩定性及吸放光性質，則是透過TGA、UV/Vis、PL來加以鑑定。在中間連接基為直線型硬端的化合物1a、1c及1d，發現具有Colh液晶相，且澄清點溫度及液晶相範圍會隨著中間連接基的長度增加而增加。而分子在液晶相時的堆疊，經過理論計算後，可知化合物1a、1c及1d在單位晶格為9 ?的高度內，皆含有3 - 4個分子，且推測都是由一個分子組成一個圓盤，再進而堆疊成Colh。在系列化合物的吸放光性質，發現所有曲線皆與前驅物2相近，顯示其吸放光特性皆是由quinoxaline雜環結構所主導，量子產率於0.52 - 0.61之間。系列二主要探討內容為成功設計並合成一系列結合quinoxaline雜環與1,3,4-oxadiazole/1,3,4-thiadiazole結構之盤狀液晶分子，並探討置換氧、硫原子及碳鏈長短對於液晶行為之影響。利用FT-IR、POM、TGA、DSC、XRD、UV以及PL等儀器針對系列化合物之物理及化學性質加以探討。在系列二中，化合物3a至5a皆可觀察到Colh液晶相。統整所有結果後，發現在系統中增加一-OH基或是改變結構之平面性，將可增加其澄清點溫度及液晶相範圍，有效提升液晶性質。而系列分子在液晶相時的堆疊，推測為由兩個分子以頭對尾的方式組成一圓盤，在單位晶格為9 ?的高度內，存在2 - 3個圓盤，再進而堆疊成Colh。最後，在UV、PL的部分，發現化合物3a及5a，其吸放光性質皆由quinoxaline雜環結構主導，而在化合物4a的部分，則由於共軛系統增大，使得吸放光波長皆有所紅位移。 Series I A novel system of symmetric dimers containing quinoxaline units has been synthesized and their mesomorphic behavior investigated. All compounds were characterized by 1H, 13C-NMR spectroscopy and the mesomorphic behavior of these compounds investigated by polarized optical microscopy, differential scanning calorimetry and powder x-ray diffraction. The formation of mesophases was found to be sensitive to the number of carbon length of the side chains and/or the spacer. The results indicated that compound 1a, 1c and 1d exhibited hexagonal columnar phases. Packing studies indicated that a single molecule was required to generate a disc-like correlated structure in the columnar phases. The UV and PL spectra were also studied for their light-emitting properties.Series II A new system of 1,3,4-oxa(thia)diazoles contaning quinoxaline exhibiting mesomorphic properties was synthesized and their mesomorphic properties examined. These molecules exhibited hexagonal columnar phases. A change of alkoxy chains and oxygen/sulfur atoms incorporated was amied to their difference or effect on the formation of mesophases. The formation of columnar phases was strongly sensitive to the central heteroatoms and/or their positions incorporated. Packing studies indicated that two molecules laid side-by-side to required to generate a more disc-like correlated structure in the columnar phases. However, these materials show great potential for electronic devices.
Appears in Collections:	[Graduate Institute of Chemistry] Electronic Thesis & Dissertation

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