Prepare And Characterization Of Electrochromic Materials Based On Thiophene And Carbazole Derivatives

As one of the environmental protection materials,electrochromic(EC)materials have been attracting great deal of interest due to their potential applications in the fields of smart windows,displays and sensors.Most recent studies on EC materials are devoted to conducting polymers because of their superior EC properties,such as better processability,faster switching and color tunability.Carbazole and thiophene derivatives are the most excellent monomer materials.In order to get multicolor electrochromic polymers,we prepared a series of monomers based on carbazole and thiophene and studied the effect of molecular structure on the elechrochromic properties of the polymers.We introduced functional groups,donor-accept structure and star structure into monomers which were based on carbazole and thiophene,and their polymers were successfully synthesized by electropolymerization.Electrochromic devices base on polymer films were prepared and the their electrochromic properties were studies in detail.In the first part of our dissertation,homopolymer(PTBC)based on 9-(4-(thiophen-3-yl)-phenyl)-9H-carbazole(TBC)and its copolymer(P(TBC-EDOT))with EDOT could show two colors and five colors respectively.P(TBC-EDOT)film presentedreasonable optical contrast(36.6%at 1100nm)and fast switching time(1.9 s at 474 nm)?Besides,Cyclic voltammetry studyindicated that the P(TBC-EDOT)film kept stable up to 300 cycles and the redox curvesonly showed a slight shrinkageafter 300cycles,which implied that P(TBC-EDOT)film has a reasonable redox stability.In the second part,A novel ferrocene-containingcompound named 6-(3,6-di(thiophen-2-yl)-9H-carbazol-9-yl)hexyl ferrocenecarboxylate(BTC-H-Fc)wassynthesized by simple chemical route,and 3,6-di(thiophen-2-yl)-9H-carbazole(BTC)was prepared for comparison.Both of thehomopolymers of BTC-H-Fc and BTC were successfully synthesized by electropolymerization and kept the redox activity uponrepeated cycling.Compared to PBTC which could only show two colors,P(BTC-H-Fc)film could exhibit four colors as a consequence of mixing the colors of main chain and Fc group.Meanwhile,P(BTC-H-Fc)film presented higher optical contrast of 52%(at 1000 nm)and reasonable switching time(4.1 s at 1000 nm),which due to the electrochromic Fc group.In the third part,we synthesized a novel star structure monomer:1,4-bis(3,6-di(thiophen-2-yl)-9H-carbazol-9-yl)benzene(BTCPh).Its homopolymer(P(BTCPh))and copolymer(P(BTCPh-EDOT))with EDOT were prepared by electropolymerization.P(BTCPh)film displayed four colors,while,P(BTCPh-EDOT)could exhibit five colors include three-primary colors which was meaningful to the practical application of electrochromic polymers.Besides,P(BTCPh)film has preferable optical contrast(48.9%at 1100 nm)and switching time(1.5 s at 660 nm).P(BTCPh-EDOT)also present high optical contrast(47.2%at 1100 nm)and reasonable switching time(2.5 s at 679 nm).