The study of synthesis and characteristics on Schiff''s based liquid-crystalline compound

• Main Authors: Chih-Sen Yang, 楊織森
• Other Authors: Jui-Hsiang Liu
• Format: Others
• Language: zh-TW
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/22056945566286534412

碩士 === 國立成功大學 === 化學工程研究所 === 81 === Schiff''s base 系液晶化合物是以(-CH=N-)為中間連接基(Bridging group)之化合物。本實驗一共合成四種含有不同末端取代基之此型化合物 ，並探討其特性的差異。四種末端取代基之中，包括兩種推電子基團(CH3 O-，C3H7O-)及兩種拉電子基(F-，CN-)。由實驗結果發現:對於分子鏈長 較短之產物I,皆無液晶狀態的出現,其原因可能是分子太短使得分子間的 引力太強,造成無液晶現象的出現。但當此系列之產物 I 接上間距( Spacer)之後,則分別出現不同的液晶狀態，其原因可能是產物II分子的分 子長度的增加,使得分子側面的引力與分子末端的引力達成某種平衡,因而 出現液晶現象.綜合實驗結果發現:分子的長度對於液晶的存在與否影響重 大,而且如果分子長度太短,則末端基團是否為推拉電子基團,對於液晶狀 態的存在與否,則無決定性的影響.另外,上述產物之單體化及聚合反應亦 有概略性的探討. The Schiff''s base liquid-crystalline compound contained a (-CH= N-) bridging group. A series of these compounds containing four different terminally substituted groups were synthesized and their characteristics on liquid crystalline were investiga- ted. Four terminally substituted groups, two electron-donating groups (CH3O,C3H7O) and two electron-withdrawing groups (CN, F) were selected in this investigation. It''s found that the short molecular length compound I had no liquid crystalline charac- teristics. The results suggest that the short molecular length models existed a large molecular interaction and the packing of the molecules into crystal lattice increased, which destroyed the structure of the liquid crystalline. When a spacer was introduced,however, they showed liquid crystal characteristics. A molecular interaction balance between the molecular side and terminal interactions may be achieved, when the molecular length was increased. Our results showed that the molecular length is an important factor for the existence of the liquid crystalline. Short mole- cular length models will have no liquid crystal characteristics and which are independent of the existence of the electron- donating and/or electron-withdrawing groups.