Study on the Influences of the Intramolecular Hydrogen Bond and Fluoro Substituent on the Mesophase Behaviors of Schiff-based Liquid Crystals

• Main Authors: Tzu-yang Chiang, 江子揚
• Other Authors: Chiung-Cheng Huang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/j25bjp

碩士 === 大同大學 === 化學工程學系(所) === 102 === In this article, four novel homologous series of chiral Schiff base liquid crystals designed and synthesized to investigate the effect of fluoro substituent, intramolecular hydrogen boning, the variation of achiral tail to investigate the mesomorphic properties of Schiff base molecules. The mesomorphic properties and their corresponding transition temperatures were primarily characterized by the microscopic textures and DSC thermograms. The first series of compounds CTCmN (m=6-8) exhibit the phase sequence: Iso.–BPI–N*–SmA*–Cr. and compound CTCmN (m=8) possesses the widest temperature range of the BPI phase (2.6 °C). Fluoro-substituted compounds CTCmNF (m=6-8) exhibit the phase sequence: Iso.–N*–SmA*–Cr., It can be seen that the introduction of fluoro substituent into the salicylaldimine core results in the suppression of BP phase. The results of the second series show that compounds CTYmNF (m=6-8) with linear alkynyl chain exhibit the phase sequence: Iso.–N*–SmA*–Cr. and compound CTYmNF (m=7) possesses the widest temperature range of the nematic phase (44.46 °C). In addition, compound CTYmNF (m=6) possesses the widest temperature range of the SmA* phase (83.56 °C). The third series of compounds CTOCmNF (m=6-8) with alkoxy tail exhibit the phase sequence: Iso. – N* – SmA* – Cr.. The results of the fourth series showed that Schiff base compounds CTC8HN and CTY8HN without hydroxyl group exhibit the phase sequence: Iso.–BPI–N*–SmA*– Cr.. Moreover, fluoro-substituted Schiff base compound CTC8HF exhibits the phase sequence: Iso.–N*–TGBA*–SmA*–Cr., indicating that the introduction of fluoro substituent into the rigid core of Schiff base compound with alkyl chain induce the TGBA* phase formation. However, both of fluoro-substituted Schiff base compound CTY8HF with linear alkynyl chain and CTOC8HF with alkoxy tail exhibit the phase sequence: Iso.–N*–SmA*– Cr. and have no the TGBA* phase formation. It can be seen that the incorporation of fluoro substituent into Schiff base compounds with linear alkynyl chain or alkoxy tail suppresses the formation of the frustrated phase.