Electrochemical Synthesis And Characterization Of D-A Type Conducting Polymers Containing Pyrido[4,3-b]pyrazine Group And Thiophene Derivatives

Conducting polymers(CPs)have become new indispensable materials due to their unique properties such as attainability of faster response times,higher contrast ratios,color tenability via structural modification and easy processibility.And many researchers have focused on the preparation,properties and application of CPs.As an important class of new conductive polymer materials,polythiophene and its derivatives have attracted large attention because of their excellent properties,such as ease of chemical and electrochemical synthesis,redox stability,and processability,which made them possess great potential application value.In this article,a series of thipthene based D-A type monomers were synthesized via coupling reaction and electrochemical polymerization and their electrochemical and optical properties were investigated.To be specific,in this thesis,5,8-dibromo-2,3-bis(4-(decyloxy)phenyl)pyrido[4,3-b]pyrazine was synthesized and used as the acceptor unit,which then be coupled with six thiophene derivatives to give rise to six novel monomers via Still coupling reaction.The corresponding polymers were obtained by electropolymerization method in acetonitrile or acetonitrile/dichloromethane solution containing tetrabutylammonium hexafluorophosphate(TBAPF6)as a supporting electrolyte.These polymers were characterized in terms of their spectroelectrochemical and electrochemical properties by cyclic voltammetry,fourier transform infrared spectroscopy(FT-IR),UV-Vis-NIR spectroscopy and scanning electron microscopy(SEM).Experimental results revealed that all the six polymers have showed distinct electrochromic properties,good stabilities,satisfactory coloration efficiency,fast respond times and high optical contrasts.What is more important,the band gaps of the six polymers were relative low,especially for the polyemers PMOTPP and PETPP(1.136 eVand 0.92 eV,respectively)and the tunableness of the band gap can be realized,which made them to be useful in applications in electrochromic devices.In addition,in this thesis,two donor-acceptor systems,4,7-Bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)2-dodecyl-2H-benzo [1,2,3] Triazole(M1)and 2,3-di(5-methylfuran-2-yl)-5,8-bis(2-(3,4-ethylenedioxythiophene))quinoxaline(M2)were synthesized according to the reported papers and used to attain a low band gap neutral black copolymer P(1-co-2).Then the electrochemical and electrochromic properties of the copolymer were studied.Electrochromic investigations showed that the copolymer exhibited a deep black color at neutral state,which absorbs virtually the whole visible spectrum(400–800 nm),and switched to a transmissive grey color when oxidized.This color change was few reported in the literatures which made the copolymer to be a new type electrochromic material and have high value of potential application.