Synthesis And Characterization Of Triphenylene Discotic Liquid Crystals Molecules Having Functional Groups

Discotic liquid crystals can self-assemble to give highly ordered hexagonal columnar mesophase, which exhibit high anisotropic charge carrier mobility and show huge potential application as organic photoelectronic materials. Much research work has been spent on improving the charge carrier mobility of triphenylene-based liquid crystals through structural modifications designed to increase the columnar ordering in terms of the average length of ordered stacking arrays along the column. The introduction of fluorinated substituents or amide function groups which may provide hydrogen bonding is commonly used to enhance the attractive interactions between the discotic mesogens. Additionally, if the liquid crystal can be solidified through cross-linking bonds, the high charge carrier mobilities and enough mechanical intensity should be obtained, however, concerning studies in this field has rarely been done. This thesis reported the synthesis and characterization of novel discotic liquid crystal molecules based on triphenylene core by introducing functional groups which can be cross-linkable. The prinspal elements are as follows:1. Symmetrical substitution triphenylene molecule C18H6(OC7H14COOH)6 having carboxylic acids at the peripheral chains was prepared by three steps starting from o-benzenediol and ethyl 8-bromooctanoate.2. A triphenylene derivative, C18H6(OC3H6OH)6, having six hydroxy groups at the peripheral chains was synthesized and characterized. TGA and DSC showed that this compound had good thermal stability. DSC analysis and POM texture observations revealed that this triphenylene derivative exihibited mesophases both during heating and cooling, and showed column phase when cooled to 256℃.3. Modification of C18H6(OC3H6OH)6 with succinic anhydride was undertaken, giving the new product, C18H6(OC3H6OCOC2H4COOH)6, which has six carboxylic acid groups at the peripheral chains. TGA and DSC showed that the compound have a lower weight loss temperature and melt point than C18H6(OC3H6OH)6. However, POM observations revealed that it didn't showed mesophases.C18H6(OC3H6OH)6 was also reacted with (2-chloroethoxy)ethene to prepare another derivative,C18H6(OC3H6OCH2CH2OCH=CH2)6.