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    A new conducting polymer of 2,5-bis(2-thienyl)-1H-(pyrrole) (SNS) containing carbazole subunit: Electrochemical, optical and electrochromic properties
    (Elsevier Science Sa, 2009) Koyuncu, Sermet; Zafer, Ceylan; Sefer, Emre; Baycan Koyuncu, Fatma; Demiç, Şerafettin; Kaya, İsmet; Özdemir, Eyüp
    We report here the synthesis of a new electroactive monomer 3,6-di-tert-butyl-[4-(2,5-di-2-thienyl-1H-pyrrol-1-yl)phenyl]-9H-carbazole in five steps and polymerization of this monomer by two different procceses: Kumada Coupling and electro-oxidative. The product obtained by chemical polymerization exhibits a high thermal stability and narrow molecular weight distribution. While, in the UV-vis absorption spectrum of monomer the absorption peaks appear at 338 nm, the chemically synthesized polymer absorbs at 428 nm with 90 nm red shift. Cyclic voltammogram of monomer shows two separate oxidation processes which reflect the first oxidation at +0.84 V and a second one at +1.43 V. When the polymeric film prepared by electrochemical process was subjected to a repeated cyclic scan between -0.2V and +1.0V, it switches among three different colors (orange, green and blue). The oxidation and reduction response times were calculated as 2.0 s for this polymer film and exhibits high redox stability. The results anticipate that this kind of polymers can be used for designing electrochromics based on the use of one molecule for the generation of three basic colors (RGB). (C) 2009 Elsevier B.V. All rights reserved.
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    Electrochemical, optical and electrochromic properties of imine polymers containing thiophene and carbazole units
    (Elsevier Science Sa, 2009) Koyuncu, Sermet; Kaya, İsmet; Baycan Koyuncu, Fatma; Özdemir, Eyüp
    New imine polymers containing thiophene and carbazole moiety were synthesized by using both chemically oxidative in the presence of FeCl3 and electrochemically oxidative process. While UV-vis, FT-IR, H-1- and C-13 NMR techniques were used for the structural characterization, the number-average molecular weight (M-n), weight-average molecular weight (M-w) and polydispersity index (PDI) values were determined by size exclusion chromatography (SEC). The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) energy levels, electrochemical (E-g') and optical band gap (E-g) values were calculated by using the results of cyclic voltammetry and UV-vis absorption spectroscopy measurements, respectively. Spectroelectrochemical measurements were carried out against the changes in the optical properties of conducting polymers upon voltage changed. Also the yellow color of film changed to green color with applied potential. Conductivities of these polymers were determined by using four-point probe technique. It was seen that the conductivities were increased by iodine doping. (C) 2009 Elsevier B.V. All rights reserved.