The Synthesis And Characterization Of Novel 2,3-dithienylquinoxaline Conjugated Polymers

In this thesis, we report a new synthesis of novel 5,8 -dibromo-2, 3-dithienylquinoxaline molecule using thiophene, Oxalic acid chloride, benzothiadiazole as starting materials. The structure of the intermediates was verified by 1H and 13C NMR technologies. We also have successfully synthesized two novel D-A type conjugated polymers via Suzuki Coupling reaction using 5,8-dibromo-2,3-dithienylquinoxaline as acceptor, fluorine/carbazole as donoer. We also measured and researched their UV-vis absorption and fluorescence emission properties, thermal stability and molecular weight. On the other hand, we also sythesiezed a new monomer 2,3,5,8-tetrathienylquinoxaline using thiophene to replace the 5,8-bit of bromine atoms. We also prepared a novel polymer by electrochemical polymerization method. And the electrochemical characteristics and UV-vis absorbtion properities of the new polymer have been studied.The new molecule 5,8-dibromo-2,3-dithienylquinoxaline was prepared via 4 steps starting from thiophene, Oxalic acid chloride, benzothiadiazole, the total Yeild was 78.6%. A Suzuki coupling reaction between 5,8-dibromo-2, 3-dithienylquinoxaline and two different boric acid esters afforded our target polymers. We verified the struture of the intermediates by 1H and 13C NMR., and verified the construction of the two new polymers by IR technologies. Their UV property and fluorescence property were characterized by UV-vis and fluorescence spectroscopy respectively. The maximum UV-vis absorbtion peak of two polymers was between 280nm-500nm. The highest fluorescence emission peak of the two polymers in choloform solvent was respectively 551nm and 580nm. The band with was 2.44 and 2.41 repectively by calculation. The molecular weight was measured by GPC. The Mn of the two polymers were 4521 and 2159. Their thermal stability was tested by thermogravimetric analyzer. The temperature was 261.7℃ and 180.6℃ repectively when the weight loss ratio is 5%.The novel monomer unit 2,3,5,8-tetrathienylquinoxaline was prepared by 5,8-dibromo-2,3-dithienylquinoxaline and 2-thiophene boric acid, using the Suzuki coupling reaction. Its structure has verified by 1H and 13C NMR technologies. The new polymer basied on this novel monomer unit was synthesized by electrochemical polymerization method. Monomer’s initial oxidation potential is 1.04V, and reduction potential is-0.71V. The polymer’s initial oxidation potential is 0.44V, and reduction potential is-0.85V. In the process of continuous potential scan, the scan line of the polymer film can form a whole cycle which means the OX-RED process is reversible., which shows that the electrochemical characteristic of this new polymer was relatively stable. We also studied the UV-vis property of the polymer in ITO glass. It showes the absorption of the polymer was between 500nm-800nm, which was suitably matched the wavelength of visible light. This has provided a theoretical basis for its future application...