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Atilim University,

Chemical Engineering and Applied Chemistry, ATOMSEL

Incek, Golbasi, 06836
Ankara-Turkey
Phone: +903125868304-8817
Fax: +903125868091
E-mail: cihaner@atilim.edu.tr

5. Electrical, Optical and Photoconductive Properties of Poly(dibenzo-18-crown-6)

Atef F. Qasrawi, Atilla Cihaner and Ahmet M. Önal
Crystal Research and Technology, 39, 56-62 (2004)

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To investigate the energy levels, absorption bands, band gap, dominant transport mechanisms, recombination mechanisms and the free carrier life time behavior of poly-dibenzo-18-crown-6, poly-DB18C6, films, the dark electrical conductivity in the temperature range of 200-550 K, the absorbance and photocurrent spectra, the photocurrent –illumination intensity and time dependence at 300 K were studied. The dark electrical conductivity measurements revealed the existence of three energy levels located at 0.93, 0.32 and 0.76 eV below the tails of the conduction band. The main transport mechanism in the dark was found to be due to the thermal excitation of charge carriers and the variable range hopping above and below 260 K, respectively. The photocurrent and absorbance spectra reflect a band gap of 3.9 eV. The photocurrent -illumination intensity dependence reflects the sublinear, linear and supralinear characters indicating the decrease, remaining constant and increase in the free electron life time that in turn show the bimolecular, strong and very strong recombination characters at the surface under the application of low, moderate and high illumination intensity, respectively. A response time of 25.6 s was calculated from the decay of I ph-time dependence.

 
4. Electrochemical Behaviour and Electrochemical Polymerization of Fluoro-Substituted Anilines

Atilla Cihaner and Ahmet M. Önal
Polymer International, 51, 680-686 (2002)

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The electrochemical behaviour of three fluoro-substituted aniline monomers, 2-fluoroaniline (2FAN), 3-fluoroaniline (3FAN), 4-fluoroaniline (4FAN), was investigated in aqueous acidic and organic media by means of cyclic voltammetry (CV) studies. Constant potential electrolysis (CPE) of the monomers in acetonitrile-water mixture (1:1 by volume) using NaClO4 as supporting electrolyte yielded soluble polymers. The mechanism of electrochemical polymerization was investigated using in situ electron spin resonance (ESR) and in situ UV-VIS measurements indicated that the polymers obtained are in the emeraldine base form. In situ ESR studies indicated that electrochemical polymerization involves a radical-cation as an intermediate. Characterization of polymer products have been carried out using FTIR and NMR spectroscopic techniques, and thermal behaviour was studied using differential scanning calorimetry (DSC). It was found that conductivity can be imparted to as-synthesized polyfluoroanilines via iodine doping.

 
3. Synthesis and Characterization of Fluorine-Substituted Polyanilines

Atilla Cihaner and Ahmet M. Önal
European Polymer Journal, 37, 1767-1772 (2001)

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Poly(2-fluoroaniline), P2FAN, poly(3-fluoroaniline), P3FAN, and poly(4-fluoroaniline), P4FAN, have been synthesized from fluorine substituted aniline monomers in aqueous acidic medium using potassium dichromate as oxidizing agent. Characterization of polymer products has been carried out using FTIR, and NMR spectroscopic techniques. Thermal analysis of polyfluoroaniline powders was also investigated using differential scanning calorimetry and thermogravimetric analysis. To compare the structural properties of the polymers, polyfluoroanilines were also synthesized using ammonium peroxydisulfate as oxidizing agent. polyfluoroanilines synthesized by chemical oxidation were doped using iodine and the charge in the paramagnetic behavior was monitored by electron spin resonance spectroscopy.

 
2. Electrochemical Polymerization of 4-Allylanisole

Atilla Cihaner, Hasan N. Testereci and Ahmet M. Önal
European Polymer Journal, 37, 1747-1752 (2001)

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Electrochemical polymerization of 4-allylanisole (4AA), via constant potential electrolysis, has been investigated in acetonitrile using two different supporting electrolytes. Redox behaviour was also studied in the same solvent-electrolyte couples at room temperature. Electrochemical polymerization of the monomer yielded insoluble polymer films on the electrode surface, which bears a very low conductivity, together with the low molecular weight polymers in the bulk of the solution. The decrease in the monomer concentration, during the electrochemical polymerization, was monitored by taking the cyclic voltammogram of the electrolysis solution. The effect of temperature on the rate of electrochemical polymerization was also studied. The polymers were characterized by taking the 1H-NMR and FTIR spectra. Molecular weight of the soluble polymer was determined by vapor pressure osmometry. Thermal analysis of the polymer film and soluble polymer were done by DSC.

 
1. Electroinitiated Polymerization of 2-Allylphenol

Atilla Cihaner and Ahmet M. Önal
Polymer Bulletin, 45, 45-52 (2000)

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Redox behaviour of 2-allylphenol (2APhOH) was studied by using cyclic voltammetry (CV) and electroinitiated polymerization was conducted at the measured peak potentials. Constant potential electrolysis (CPE) of the monomer was carried out in acetonitrile-sodium perchlorate, solvent-electrolyte couple, at room temperature. Polymerization of the monomer yielded insoluble polymer films on the surface of the electrode together with the low molecular weight polymers in the bulk of the solution. The structural analysis of the polymers were carried by 1H-NMR and FTIR spectroscopy. Molecular weight of the soluble polymer was determined by GPC. Thermal properties of the polymer film and soluble polymer were studied by DSC. The course of electroinitiated polymerization was monitored by in-situ UV-VIS spectroscopy.

 
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