側環取代基與尾端側鏈對香蕉形分子液晶性質影響之研究

Abstract

繼續以前本研究室探討以酯類做為連接基的香蕉形分子的取代基效應。本論文對末端側鏈進行改變，結果顯示改變側鏈長短有可能會影響分子構形，進而造成液晶相的不同。另外採用不同的側鏈連結基，並固定碳鏈長短以比較其異同，數據顯示當連結基由烷氧基改為酯基時，液晶相範圍變大同時澄清點上升，而當改為烷基時，則不利於液晶相的產生。 另在側環（B環）上導入不同的取代基，結果發現B環上含有取代基不利於液晶相的產生，除了取代基為氟的分子有機會產生液晶相外，其他的取代基皆使得液晶相消失。最後我們將C 環改為吡啶環，結果顯示，相較於苯環，吡啶環不利產生液晶相。

A series of banana-shaped organic molecules which have a central aromatic ring (C ring) modified by different substituents and four side aromatic rings linked by ester bonds were synthesized and characterized in our earlier work. In this research, we aim toward the modification of terminal side chains on the molecules. Results show that the modification of chain length will alter the mesophases due to different molecule geometry. In addition, we modified the molecules with several different linkages but maintain the same carbon chain length. Results show that molecules with ester linkages prefer a larger mesophase temperature range and higher transition temperature between liquid crystal mesophase and isotropic phase comparing to ether linkages. Molecules with pure alkyl side chains are unfavorable to form liquid crystal mesophases. On the other hand, the addition of substitents on side ring B will diminish the appearance of liquid crystal mesophases except fluorine. Also, the replacement of central benzene ring (C ring) with a pyridine ring results in the disappearance of liquid crystal mesophases as well.