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  • 學位論文

多炔苯盤形分子與具氰基之無鏈彎曲形分子之合成及液晶性質探討

Synthesis and Liquid Crystal Properties of Multiynylbenzenes and Chainless Cyano-containing Bent-Shaped Molecules

指導教授 : 徐秀福

摘要


本論文主要分為四部分,前三部分針多炔苯盤形分子進行官能基修飾,以開發或調控盤形向列相之性質,而最後一部分則開發不具鏈但利用分子間氫鍵及分子的彎曲提供分散力之液晶材料。 第一部分為引入外圍六個羧苯基至六炔苯盤形分子上,希望藉由外圍羧基與多胜肽鏈進行偶合,形成具特殊二級結構之功能性分子。目前已成功偶合上部分取代多胜肽鏈分子,未來則可朝向偶合上六條多胜肽鏈之偶合條件。另外,此系列含羧酸化合物也與系列三含吡啶化合物經氫鍵作用力形成新的盤形向列相液晶材料。 第二部分則是引入尾端硫氫基之長碳鏈於五炔苯盤形分子的ω位置,引入硫氫基的最終目的為將此液晶分子修飾至金奈米粒子表面後,對其自發性排列之行為研究。而此系列分子的液晶性質和以前文獻中所報導ω位置尾端長鏈具取代基的五炔苯分子比較,系列二分子具有較低的液晶形成溫度及較大的液晶溫度範圍。 系列三利用在六炔苯基苯盤形分子上置換其中一側臂為吡啶炔側臂以了結其對液晶行為之影響,並期望能與含羧機之第一系列化合物形成氫鍵作用力而開發出新盤形液晶材料。將六缺苯基苯之一側臂以吡啶炔側臂取代後其熔點及澄清點同時下降約30 oC;其中澄清點的下降,避免了一般六炔苯衍生物因高澄清點溫度所導致的熱分解現象。 系列四中則開發具分子間氫鍵之無鏈彎曲形液晶材料。利用分子結構中之極性氰基端與另一分子之氫氧基端形成分子間氫鍵作用力,使得系列四化合物雖不具有一般液晶分子為了提供擾動力所必備之長碳鏈部分,亦可形成液晶相。

並列摘要


Four series of compounds are reported. The first three are based on discotic hexaynylbenzene core and the last series deals with chain-less bent-shaped molecules.. Incorporating carboxylic groups onto the peripherals of hexaynylbenzene affords, hexakis(carboxylphenylethyl)benzene, which is expected to be coupled with polypeptide chains for superstructure formation. In addition, the carboxylic groups are utilized for the formation of hydrogen-bonding with the pyridinyl group of series three compounds to show liquid crystal behaviors. In the second series, one of the peripherals in hexakis(alkoxylphenylethynyl)benzene is modified by alkylthiol in hope to be attached ontogold nanoparticles. The mesogenic behaviors of analogous compounds with different functional groups in the ω-position are discussed. In the third series, one of the side-arms of hexakis(alkoxylphenylethynyl)benzene was replaced with a pyridinylethyne. The substitution has resulted in lower melting and clearing points . In the last part of this thesis, chainless bent-shaped mesogens are prepared. For achieving mesophases, the dispersive forces are provided by the intermolecular hydrogen bonding and the bending of the core rather than the vibrational freedom of alkyl or alkoxyl chains.

參考文獻


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