Synthesis And Properties Of Poly(2’-aminomethyl-3,4-ethylenedioxythiophene) And Its Derivatives

Conducting polymers have received great attentions in the field of material science due to their important scientific potential and broad prospects in commercial applications.Among the various kinds of conducting polymers,poly(3,4-ethylenedioxythiophene)(PEDOT)is the representatives and highly promising "star conducting polymer" with several advantages such as high electrical conductivity,long-term stability,and easy processing,which make it as a good candidate in a wide range of application areas,such as super capacitor,sensor and electrochromic devices.However,its monomer 3,4-ethylenedioxythiophene(EDOT)shows low aqueous solubility and there is no active group on the side chain,which reduces the possibility of interaction with other molecules and thereby limits the application of PEDOT.Therefore,lots of researches have been focused on grafting active functional groups on the side chain of EDOT and various EDOT derivatives have been synthesized.The grafting of pendant side groups onto the EDOT backbone such as flexible chlorine methyl,hydroxymethyl and carboxyl functional groups were widely studied and reported.However,there are few reports on aminomethyl group functionalized EDOT derivatives.Research of many basic theoretical problems,performance study and the development in applications based on aminomethyl group functionalized PEDOT and its derivatives are yet immature and there is large improvement in its performances.In this study,we introduced the aminomethyl group into EDOT to form the monomer of 2’-aminomethyl-3,4-ethylenedioxythiophene(EDOT-MeNH2)and then three different EDOT-MeNH2 derivatives were synthesized.Besides,the corresponding polymers were prepared via electrochemical polymerization and the detailed characterization,properties and electrochromic performances of the resultant polymers were systematically investigated.1.Aminomethyl functionalized PEDOT derivative,poly(2’-aminomethyl-3,4-ethylenedioxythiophene)(PEDOT-MeNH2),was electrosynthesized in CH2Cl2-Bu4NPF6(0.1 M)system containing 2%BFEE.The electrochemical behavior,structure characterization,thermal properties and surface morphology of the polymer were systematically investigated by cyclic voltammetry(CV),Fourier-transform infrared spectroscopy(FT-IR),thermogravimetry(TG)and scanning electron microscopy(SEM),respectively.Besides,PEDOT-MeNH2 films exhibited the electrochromic nature with obvious color changing from purple in the reduced form to blue upon oxidation.By further investigation,kinetic studies revealed that PEDOT-MeNH2 film had decent contrast ratio(41.8%),favorable coloration efficiency(152.1 cm2 C-1)and moderate response time(2.4 s).Satisfactory results implied that the obtained PEDOT-MeNH2 film is a promising optoelectronic material and holds promise for electrochromic devices and display applications.2.The copolymerization of EDOT-MeNH2 and EDOT was successfully performed electrochemically in CH3CN + Bu4NPF6(0.1 M)by direct anodic oxidation of the monomer mixtures.A series of experiments with different monomer feed ratios were carried out to investigate the influence of monomer feed ratio on the electrochemical copolymerization and the overall properties of the copolymer films.As-formed copolymers owned both the advantages of PEDOT-MeNH2 and PEDOT,i.e.,good electrochemical behavior and excellent electrochemical stability.The band gap(extracted from the onset of the π-π*transition)of copolymer with the feed ratio of 1:1 was calculated as 1.67 eV.By further investigation,kinetic studies revealed that the copolymer with the feed ratios of 1:5 had inferior contrast ratio(10%)and coloration efficiency(58 cm2 C-1).The structure,thermogravimetry and morphology of the copolymers were investigated by FT-IR,TG,and SEM,respectively.3.A water-soluble EDOT derivative was designed by using hydrochloric modified EDOT-MeNH2(EDOT-MeNH2-HCl)and electropolymerized in aqueous solution to form the corresponding polymer with excellent electrochromic properties.Moreover,the polymer was systematically explored,including electrochemical,optical properties and structure characterization.The electrochemical polymerization of EDOT-MeNH2-HCl and EDOT-MeNH2 and electrochromic performances of the corresponding polymers(PEDOT-MeNH3+A-and PEDOT-MeNH3+ClO4-)were comparatively studied at the same condition.CV showed lower oxidation potential of EDOT-MeNH2-HCl(0.85 V)in aqueous solution,indicating that the electropolymerization of EDOT-MeNH2·HCl was more successful than EDOT-MeNH2.PEDOT-MeNH3+A-revealed higher contrast ratio(26.38%),favorable coloration efficiency(156 cm2 C-1),and faster response time(1.4 s)at the wavelength of 603 nm,while the contrast ratio,coloration efficiency and response time of PEDOT-MeNH3+ClO4-were only 13.82%,31 cm2 C-1 and 4.4 s,respectively.Satisfactory results implied that salinization can not only change the polymerization system,but also adjust the optical absorption,thereby increase the electrochromic properties.4.Two poly(3,4-ethylenedioxythienylene)(PEDOT)derivatives were successfully synthesized by electrochemical polymerization of precursors,diethyl 3’-(((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methyl)azanediyl)dipropanoate(monomer 1)and ethyl 3-(((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methyl)amino)propanoate(monomer 2),respectively.Structure-property relationships of monomers and polymers,including electrochemical,optical properties,and morphology,were systematically explored.Significantly,the designed polymers exhibited red and orange emission signatures with higher fluorescence quantum yields(ΦF)of 0.044 and 0.045 compared with monomers;they may be used as building blocks for rational design of fluorescent materials.Moreover,cyclic voltammetry and spectroelectrochemistry studies demonstrated that poly(diethyl 3’-(((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methyl)azanediyl)dipropanoate)(P1)and poly(ethyl 3-(((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methyl)amino)propanoate)(P2)can be reversibly oxidized and reduced accompanied by obvious color changes from light purple to light blue for P1,and from purple to blue for P2.Furthermore,both P1 and P2 displayed higher optical contrasts(40-70%)in the visible region,favourable coloration efficiency(typically 50-230 cm2 C-1).From these results,the two polymers would be promising candidate materials for display applications.