| Summary: | 碩士 === 國立交通大學 === 應用化學系 === 87 === Studies on the Synthesis and Properties of New Thermotropic Main Chain Liquid-Crystalline Wholly Aromatic Polyesters Derived from 2,5- Thiophene
Student : Shing Hwang Adviser:Dr. Tzuoh-Miin Juang
Institute of Applied Chemistry
National Chaio Tung University
ABSTRACT
(Keyword: 2,5-thiophenedicarboxylic acid, polyester，liquid crystalline polymer)
The goal of this study is aimed to synthesized several series of new liquid crystalline polyesters and copolyesters(LCPs) based on 2,5-thiophenedicarboxylic acid , 4,4-dihydroxybiphenyl , 4,4-dihydroxydiphenyl ether , 2,6-dihydroxynaphthalene , hydroquinone , phenyl hydroquinone and quinizarin are used as aromatic diol.
Solution condensation of 2,5-Thiophenedicarboxylic acid and corresponding diol were underwent in the presence of triphenyl phosphine, haxachloroethane and pyridine which are used as condensation agents. The synthesized LCPs were characterized by optical polarizing microscope and DSC thermogram. The structure-property relationship of the obtained LCPs is investigated.
The results demonstrate that most of the homopolyesters show no liquid crystalline properties. The one synthesized from 2,5-thiophene dicarboxylic acid and 4,4’- Dihydroxydiphenyl ether is the only one which reveals nematic phases. The reason could be due to the kink structure of 2,5-thiophenedicarboxylic acid.
The experimental results demonstrate that most of the copolyesters present a nematic liquid crystalline phase. The results could be due to the combination of both kink structures of 2,5-thiophenedicarboxylic acid and aromatic diol.
The obtained copolyesters exhibit respectively a melting point ranging from 202-340ºC.Their inherent viscosities range from 0.20 to 0.35dl/g. The results demonstrate that the synthesized LCPs show relatively high molecular weight. The obtained LCPs have potential application in the field of high performance engineering thermoplastics.
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