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Öğe A new donor-acceptor carbazole derivative: Electrochemical polymerization and photo-induced charge transfer properties(Elsevier Science Sa, 2011) Koyuncu, Fatma Baycan; Koyuncu, Sermet; Ozdemir, EyupA new donor-acceptor carbazole derivative containing N-2-(2-ethylhexyl)-1,8-napthalimide as acceptor pendant was synthesized at three steps and directly coated on to ITO glass surface by using electro-chemical process. Subsequently, electrochemical co-polymerization of this monomer was carried out by using 3,4-ethylenedioxythiophene (EDOT) as co-monomer to give electrochromic polymer film. Spectro-electrochemical studies indicated that co-polymer films exhibit relatively lower band gap than that of homo-polymer. Consequently, photo-induced energy and charge transfer properties from the donor-carbazole to naphthalimide-acceptor were studied by using cyclic voltammetry, UV-vis absorption and emission spectroscopy. (C) 2011 Elsevier B.V. All rights reserved.Öğe A New Donor-Acceptor Double-Cable Carbazole Polymer with Perylene Bisimide Pendant Group: Synthesis, Electrochemical, and Photovoltaic Properties(John Wiley & Sons Inc, 2009) Koyuncu, Sermet; Zafer, Ceylan; Koyuncu, Fatma Baycan; Aydin, Banu; Can, Mustafa; Sefer, Emre; Ozdemir, EyupWe report here electrochemical synthesis of novel soluble donor-acceptor (D-A) polymer with suitably functionalized perylenetetracarboxylic diimide dye derivative covalently linked to carbazole moiety (Cbz-PDI). The band gap, E, was measured using UV-Vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Efficient intramolecular electron transfer from carbazole-donor to perynediimide-acceptor leads to remarkable fluorescence quenching of the perylene core. Furthermore, spectroelectrochemical property and surface morphology of the polymer film were investigated. Characteristic monoanion and dianion radical bands on the UV-Vis absorption spectra attributed to the electrochemical reduction of the neutral polymer were observed. During the reduction process, red color of the film turned into blue and violet, respectively. Finally, the photovoltaic performance of the D-A double-cable polymer was checked and nearly 0.1% electrical conversion efficiency is obtained under simulated AM 1.5 solar light with 100 mW/cm(2) radiation power. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6280-6291, 2009Öğe A new imine coupled pyrrole-carbazole-pyrrole polymer: Electra-optical properties and electrochromism(Elsevier Sci Ltd, 2010) Is, Ozde Deniz; Koyuncu, Fatma Baycan; Koyuncu, Sermet; Ozdemir, EyupIn this study, imine bond coupled pyrrole carbazole pyrrole monomers were synthesized in four steps and then directly polymerized onto ITO/glass surface via potentiodynamic electrochemical process. Electrochemical and optical bad gap of these monomers and polymers were calculated by using cyclic voltammetry and UV-Vis absorption spectroscopy. Conductivity of the polymers with different alkyl side-chain was determined by using four point probe technique. Length of the side-alkyl chain influence iodine doping and also conductivity of polymers. As a result of the spectroelectrochemical measurements, the orange color of film changed to green color with applied potential and the polymer was found to be suitable material for electrochromic applications. (C) 2010 Elsevier Ltd. All rights reserved.Öğe A new low band gap electrochromic polymer containing 2,5-bis-dithienyl-1H-pyrrole and 2,1,3-benzoselenadiazole moiety with high contrast ratio(Elsevier Sci Ltd, 2011) Koyuncu, Fatma Baycan; Sefer, Emre; Koyuncu, Sermet; Ozdemir, EyupA new low band gap electrochromic polymer containing of 3-(2,5-di-2-thienyl-1H-pyrrol-1-yl)-9-ethyl-9H-carbazole (SNSC) and 2,1,3-benzoselenadiazole (BSe) moiety has been reported. Structural identification of initial compounds and product were carried out by using FT-IR and H-1 NMR spectroscopy results. The resulting polymer, poly(SNSC-BSe), was completely soluble in various common organic solvents and its weight-average molecular weight (M-w) were 9420 (PDI: 1.22). According to AFM results, the RMS (root mean surface) roughness of poly-(SNSC-BSe) was found to be 48.6 nm. Besides, the thermogravimetric analysis presented that the poly(SNSC-BSe) is moderately stable against to thermal effect with the initial degradation temperature at 182 degrees C. The lowest energy transition band maxima of poly(SNSC-BSe) was 498 nm in thin film and the optical band gap calculated from the onset wavelength of the optical absorption was 1.77 eV. On the other hand, the electrochemical band gap calculated from oxidation and reduction onset values was 1.60 eV, respectively. Finally, the electrochromic performance of the polymer film represents a high contrast ratio in the NIR region (51%), fast response time of about 1 s, high coloration efficiency (274 cm(2) C-1) and retained its performance by 94.6% even after 1000 cycles. (C) 2011 Elsevier Ltd. All rights reserved.Öğe A new multi-electrochromic 2,7 linked polycarbazole derivative: Effect of the nitro subunit(Elsevier, 2011) Koyuncu, Fatma Baycan; Koyuncu, Sermet; Ozdemir, EyupA new poly-2,7-di-2-thienyl-9H-carbazole derivative (poly(TCT-N)) bearing nitro (-NO2) subunit has been reported. The electrochemical and optical properties of TCT-N monomer and its polymer have been compared to the 9-phenyl-2,7-di-2-thienyl-9H-carbazole (TCT) standard molecule. Cyclic voltammetry revealed that TCT-N and TCT have excellent polymerization activity; due to extended conjugation with the attached thiophene unit and also their low oxidation potentials. The oxidation potential of TCT-N is higher than that of TCT, because of electro-withdrawing effect of -NO2 moiety. Besides, the TCT-N polymeric film prepared via electrochemical process exhibits a multi-electrochromic behavior compared with TCT standard molecule. The electroactive orange color of poly-TCT-N film converted respectively to green, turquoise and dark blue upon applied positive potentials. Consequently, the polymeric electrochrome exhibits multi-electrochromic behavior, high redox stability, high coloration efficiency and reasonable response time for electrochromic applications. (C) 2011 Elsevier B.V. All rights reserved.Öğe A new processable donor-acceptor polymer displaying neutral state yellow electrochromism(Elsevier Sci Ltd, 2013) Oguzhan, Eda; Bilgili, Hakan; Koyuncu, Fatma Baycan; Ozdemir, Eyup; Koyuncu, SermetWe report here the synthesis of a new solution processable neutral state yellow polymeric electrochromic material containing 2,5-bis-dithienyl-1H-pyrrole (SNS)-donor and 1,8 naphthalimide-acceptor (SNS-NI) as a subunit. The electrochemical and optical properties were investigated via cyclic voltammetry (CV), UV Vis absorption and fluorescence emission measurements, respectively. Besides, electrochromic performance of poly(SNS NI) has been compared to the both the film preparation method and poly(1-phenyl-2,5-dithiophen-2-ylpyrrole) [poly(SNS-P)] as a standard polymer. In the poly(SNS-NI), yellow color of the polymer film at neutral state converted to green and then dark blue upon the polymer film fully oxidized in the positive regime. SNS NI polymer film prepared via spin casting process exhibits a high contrast ratio in the near-IR region (Delta T% = 56% at 890 nm), a response time of about 1 s, high coloration efficiency (299 cm(2) C-1) and retained its performance by 98.6% even after 5000 cycles. Finally, the results clearly indicate that both electronic nature of the molecule and film preparation method have a major impact on electrochromic performance of these polymers. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.Öğe A novel donor-acceptor polymeric electrochromic material containing carbazole and 1,8-naphtalimide as subunit(Pergamon-Elsevier Science Ltd, 2010) Koyuncu, Fatma Baycan; Koyuncu, Sermet; Ozdemir, EyupWe report here the synthesis of a novel polymeric electrochromic material containing carbazole (Cbz)-donor and 1,8-napthalimide-acceptor as subunit. The band gap E-g was measured using UV-vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Due to intramolecular electron transfer from Cbz-donor to 1,8-napthalimide-acceptor, the fluorescence quenching was observed. When the spectro-electrochemical and electrochromic properties of polymer film were investigated, various tones of green color were obtained on the polymeric film. In the positive regime, the polymer film obtained thereby is dark green resulting from the association of carbazolylium cation radicals at oxidized state and then it can be bleached by electrochemical reduction. Besides, in the negative regime, yellowish green color of film converted to blue attributed to reduction of the 1,8-napthalimide moiety. Finally, the polymeric electrochromic exhibits multi-electrochromic behavior, high redox stability, high coloration efficiency and reasonable response time. (C) 2010 Elsevier Ltd. All rights reserved.Öğe The New Branched Multielectrochromic Materials: Enhancing the Electrochromic Performance via Longer Side Alkyl Chain(Amer Chemical Soc, 2011) Koyuncu, Fatma Baycan; Sefer, Emre; Koyuncu, Sermet; Ozdemir, EyupWe describe the synthesis and structure property relationships of two branched electroactive monomers containing carbazole core, 2,5-di(2-thienyl)-1H-pyrrole, differentiated by the length of side alkyl chains (DSNSC-1 and DSNSC-2). Structural identification of initial compounds and products were carried out by using FT-IR and H-1 and C-13 NMR spectroscopy. The electroactive materials DSNSC-1 and DSNSC-2 were directly coated on to ITO glass surface by using electrochemical polymerization process. The results clearly indicate that the length of side alkyl chain has a major impact on optical and electrochemical properties of these polymers. Poly-DSNC-2 with longer side alkyl chain exhibits a high contrast ratio (Delta T% = 68% at 850 nm), a response time of about 0.8 s, and high coloration efficiency (352 cm(2) C-1) and retained its performance by 97.1% even after 5000 cycles.Öğe Toward Purple-to-Green-to-Transmissive-to-Black Color Switching in Polymeric Electrochrome(Amer Chemical Soc, 2014) Karabiyik, Elif; Sefer, Emre; Koyuncu, Fatma Baycan; Tonga, Murat; Ozdemir, Eyup; Koyuncu, SermetA novel 3,4-ethylenedioxythiophene (EDOT)-based donoracceptor electroactive monomer (HCQE) bearing carbazole subunit is synthesized, and then the corresponding polymer, poly(HCQE), is directly deposited onto ITO/glass surface via electrochemical process. Spectroelectrochemical studies demonstrate that poly(HCQE) is capable of showing both n- and p-doping processes. Hence, this low band polymer serves the multielectrochromic feature at three separate states (-0.4 to -2.0 V, -0.4 to 1.2 V, and 1.2 to 2.0 V) with a highly unique near colorless and colored states, fast switching times, redox switching stability, and exceptional transmittance change. To the best of our knowledge, this is the first report of a neutral state green multielectrochromic polymer exhibiting successive switching of colored-to-bleached-to-colored in three distinct regimes.
