Elif Altürk Parlak

Characterization of Micrometer-Sized Thin Films of Electrocoated Carbazole with p-Tolylsulfonyl Pyrrole on Carbon Fiber Microelectrodes

Carbazole (Cz) monomers with p-tolylsulfonyl pyrrole (pTsp) (used as self-dopant) were electrochemically coated onto micrometer-sized carbon fiber by potentiodynamic method. The resulting micrometer-sized thin films of homopolymer and copolymers were characterized by using electrochemical methods (i.e., cyclic voltammetry), solid-state conductivity measurements (four-point probe), spectrophotometric methods (in situ spectroelectrochemistry), Fourier transform infrared reflectance spectroscopy, and scanning electron microscopy. Cyclic voltammetric results indicate that an increase of pTsp concentration in copolymer formation (while the Cz concentration was kept constant) current density increases randomly. The maximum anodic current density was obtained as 0.49 μA cm -2 by the initial feed ratio of [pTsp] 0 /[Cz] 0 = 5. This is three times higher than the anodic current density of polycarbazole (PCz) (0.15 μA cm -2 ). The electrocoated copolymer corresponding to an initial feed ratio of [pTsp] 0 /[Cz] 0 = 5 was observed as polaron and bipolaron on indium tin oxide (ITO) by UV-vis spectrophotometry. The solid-state conductivity was measured with a four-point probe apparatus. Results show that a tenfold increase in Cz concentration leads to an increase in conductivity from 0.08 to 6.36 mS cm -1 , and also raises yields from 13.69% to 97.72%. In contrast, a 10 times increase in pTsp concentration leads to a decrease in conductivity from 0.39 to 0.02 mS cm -1 , and also decreases yields from 21.72% to 2.82% which is due to the polymers bulky structure. The efficiency of the electropolymerization process on the carbon fiber surfaces by cyclic voltammetry, depending on the experimental conditions, was evaluated to ascertain the effects of copolymer thickness, dopant, optical bandgap (Eg), and the redox parameters (anodic and cathodic potentials, E a ,E c ), oxidation peak potentials, E ox, and stability test of electrodes.

Comparative Study of Chemical and Electrochemical Copolymerization of N-Methylpyrrole with N-Ethylcarbazole Spectroscopic and Cyclic Voltammetric Analysis

ABSTRACT The copolymerization of N-Methylpyrrole (N-MPy) and N-ethylcarbazole (ECz) by chemical and electrochemical methods is investigated in detail. Random copolymers of poly[N-Methylpyrrole-N-ethylcarbazole], P[N-MPy-co-ECz], were synthesized in the presence of ceric ammonium nitrate (CAN) in acetonitrile. Electrocopolymerization of N-MPy, and ECz was carried out in various solvents on platinum electrode. Propylene carbonate (PC) was found to be the most suitable solvent for film formation. The effects of sweep rate, supporting electrolyte type, mole ratio, and temperature on the electropolymerization were discussed. The electrochemical properties of Poly(N-ethylcarbazole), (PECz) were improved on copolymerizing it with N-MPy. A copolymerization mechanism has been suggested. The resulting copolymer was characterized by UV-Vis and FT-IR spectroscopic methods, as well as cyclic voltammetric measurements.

ELECTROCHEMICAL COPOLYMERIZATION OF N-METHYL PYRROLE WITH CARBAZOLE

Electrocopolymerization of N-methylpyrrole (NMePy) and Carbazole (Cz) was conducted in acetonitrile. Oxidative chemical random copolymerization of NMePy and Cz was also realized by Cerium (IV) ammonium nitrate (CAN) for comparison. The properties of the resulting copolymers were investigated by spectroscopic methods (UV-VIS, FT-IR), cyclic voltammetry and four point probe conductometer, to understand the oligomeric pyrrole ring interaction with carbazole ring where the reactive nitrogen of pyrrole ring was capped (substituted) by methyl group.