A. Sezai Saraç

Oxidative polymerization of N‐substituted carbazoles

Poly(N-vinylcarbazole), poly(N-carbazole) and poly(N-ethylcarbazole) powders were chemically synthesized by the reaction of ceric ammonium nitrate (CAN) with N-vinylcarbazole carbazole and N-ethylcarbazole in acetonitrile. Products were characterized by elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and viscosity, X-ray fluorescence and four-probe conductivity measurement. It is found that when a suitable concentration of CAN is used in the polymerization process, the conductivity of chemically synthesized polymers can be improved further by controlling the CAN addition.

Structural Study of Pyrrole-EDOT Copolymers on Carbon Fiber Micro-Electrodes

Copolymer films of pyrrole and 3,4-ethylenedioxythiophene (EDOT) were synthesized electrochemically on the carbon fiber microelectrodes (CFME). Deposition conditions on the carbon fiber and influence of the monomer concentrations to the copolymerization as well as the electrochemistry of the resulting polymers and copolymers were studied using cyclic voltammetry, in-situ spectroelectrochemistry, FTIR-ATR and scanning electron microscopy. Effect of the monomer ratio on the formation of the copolymer was reported. The electroactivity and very well defined electrochemistry of both polymers polypyrrole and PEDOT, and copolymer of pyrrole and EDOT on the CFME as much as the Pt electrode pioneers the possibility of using these coated electrodes for bio-applications. A high level of stability to overoxidation has also been observed for PEDOT as the polymer on the CFME substrate show limited degredation of their electroactivity at potentials 1.2 V above its half-wave potential.

Electrochemical polymerization of pyrrole in acrylamide solution

Abstract Electrochemical polymerization of pyrrole (Py) in an excess of acrylamide (AAm) was accomplished by using an acetonitrile–tetraethyl ammonium perchlorate (TEAPC) solution containing both monomers. Characterization of soluble and insoluble products was carried out via FT-IR spectrum, cyclic voltammogram (CV), UV–visible spectrum, scanning electron microscope (SEM), differential scanning calorimetry (DSC) and elemental analysis. The role of monomer concentrations on the formation of resulting polymer was investigated. Since the polymerization rate of Py is faster than that of AAm, the appropriate ratio of concentrations of monomers have chosen to have chance to interact AAm with Py oligomers which was formed immediately on the electrode surface. Inclusion of AAm to polymer and the mole ratio of resulting product was reported.

Water-soluble polypyrroles by matrix polymerization : Interpolymer complexes

A new class of water-soluble polypyrroles (PPy) has been developed. This was accomplished by oxidative matrix polymerization of pyrrole (Py) monomer with Ce(IV) in the presence of poly(acrylic acid (PAA), poly(vinyl pyrrolidone) (PVP), and copolymers (CP) of vinyl pyrrolidone(VP) with acrylic acid (AA) [VP/AA; 25/75 ( CP 1 ), 50/50 ( CP 2 ), 75/25 ( CP 3 )]. The soluble and insoluble interpolymer complexes were observed according to the nature ( and conformation ) of polymers in mixture, the ratio of components, and the pH of solutions. The role of PAA, PVP, CP, Py, and Ce(IV) concentrations, the order of component addition, and the pH of the solutions were investigated. The evidence and structural reasons for the formation of soluble interpolymer complexes of PPy with different polymers are discussed. It is proposed that the compactization of the polymer matrix as well as the disturbance of the regularity of reactive groups on the polymer chain decreases the possibility of formation of soluble interpolymer complexes.

Conductometric determination of the end group ionization in acrylamide and acrylonitrile polymers initiated by carboxylic acids

Abstract The end group analysis both for polyacrylamides and polyacrylonitriles initiated by Ce(IV)-malonic acid, tartaric acid and citric acid redox systems was carried out by using conductometric titration. Carboxyl end groups of these polymers are determined by dissolving polyacrylamides in water, polyacrylonitriles in dimethylformamide and ethylene carbonate-propylene carbonate (80/20 by weight) at 25° and titrating with aqueous sodium hydroxide, alcoholic sodium hydroxide and tetrabutylammonium hydroxide, respectively. The number average molecular weight results are compared with the viscometric ones. It was found that these are in good agreement with each other. In addition to the experiments with conductometric titrations, calculations were made to find the ionization constant of carboxylic acid end groups in acrylamide and acrylonitrile polymers. For this purpose the Ostwald dilution law was used.

In situ spectroelectrochemistry and colorimetry of poly(pyrrole-acrylamide)s

Electropolymerization of pyrrole in the presence and absence of acrylamide was accomplished. Characterization of the soluble and insoluble products was carried out by using UV-visible and FTIR spectroscopy, cyclic voltammetry, colorimetry and four-point probe technique. Role of applied electrical conditions and effect of the presence of acrylamide on the formation of polymers in the solution and on electrode surface were investigated. Conductivity of polypyrrole and poly(pyrrole-acrylamide) free-standing films show a conductivity of 90 and 1.0 S/cm, respectively. Incorporation of the acrylamide to the resulting polymer was supported by electrochemistry, colorimetric and spectroscopic results. The presence of the acrylamide in the resulting polymer affects some of the properties of the polymer film (i.e., color, conductivity, electrochemistry, spectroelectrochemistry, etc.) that may bring some advantages for practical applications.

Electro-induced oxidative polymerization of N-vinylcarbazole

WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW In this study, a novel procedure to increase the yield of the non-crosslinked, photoconductive, white form of linear poly(N-vinylcarbazole) (LPVCz) is reported. The yield of LPVCz is increased (up to 53%) by the addition of catalytic amounts of ceric ammonium nitrate as an oxidant during the electrochemical polymerization of Nvinylcarbazole in a divided electrochemical cell. The concentration of Ce(IV) remained constant during the polymerization since Ce(III) is readily oxidized to Ce(IV) electrochemically. Since the electrochemical oxidation of Ce(III) to Ce(IV) took place simultaneously at the anode, the deposition of dark green crosslinked polyvinylcarbazole on the electrode surface, which hinders the formation of white LPVCz, can be prevented. The Fourier transform infrared, ultraviolet±visible and fluorescence spectra of white LPVCz showed that the structures of polymers are the same as those produced by conventional polymerization. Copyright  1999 John Wiley & Sons, Ltd.

Electrochemically induced redox polymerization of acrylamide

Polymerization of acrylamide (AA) has been studied in aqueous solution in the presence of Ce(IV) salt-oxalic acid initiator system in an electrochemical cell with and without separation of anolyte and catholyte. For reactions that required the cathode and anode sections to be analyzed individually, a cell whose compartments were divided by a sintered glass disk of the medium porosity was employed. Polymerization was initiated by a free radical that is formed by the fast reaction of oxalic acid and Ce(IV). The electrolysis of the reaction solution results in regeneration of Ce(IV), which can oxidize oxalic acid to produce radicals. The effect of sulfuric acid and cerium (IV) salt concentration and temperature on the yield of electroinitiated polymerization in different cell designs and structural identification of products were performed. Reaction was also followed by cyclic voltametric measurements, and a mechanism was proposed. Results indicated that the electrolysis method with a divided cell (85% conversion) shows advantages, compared with nonelectrolytic (5% conversion) and with undivided electrochemical cell (25% conversion) methods where a high concentration of initiator was used.

N‐Vinylcarbazole‐Acrylamide Copolymer Electrodes Electrochemical Response to Dopamine

Copolymers of N-vinylcarbazole and acrylamide were synthesized by the free radical polymerization using AIBN as initiator. Copolymer electrodes were prepared by casting from 3% solution on platinum and stainless steel substrate. Solvent was removed by heating at 1 10°C in vacuum 10 - Pa for 5 h. The response of electrodes to dopamine was tested by cyclic voltammetry and results suggest that depending on conditions (i.e., scan rates, thickness of film, composition of copolymer), the electrode shows reversible and stable behavior during the 14 days and it seems to he a suitable sensor electrode to dopamine. Stability of copolymer coating was investigated for stainless steel electrodes in sulfuric acid and it is found that copolymer coating can inhibit the corrosion of stainless steel up to 94%.

Structural definitions for soluble portions of polyacrylamides synthesized with Ce(IV)–chelating agent redox systems

Polymerizations of acrylamide initiated by ceric ammonium nitrate and ceric sulphate in combination with nitrilotriacetic acid, ethylene diamine tetraacetic acid, diethylene triamine pentaacetic acid and 1,2-cyclohexane dinitrilotetraacetic acid were studied in aqueous nitric acid and sulphuric acid solutions at 55°C in the presence of air. The experimental results can be explained by assuming that the complexes of Ce(III) with sulphate and nitrate ions, C(SO 4 ) n x(+ or -) and Ce(NO 3 ) n x(+ or -) , have different reactivities in the reactions. FTIR and UV spectra of the polymers, together with conductometric and gravimetric measurements, clearly showed that in the case of sulphato-cerate complexes, there were complexes not only on the end-groups but also on amide groups within the chain. Furthermore, it was observed that the stabilities of the primary radical sources generated by the redox pairs used in this work depend on the anion type and concentration of the acid and oxidation agent.