The growth mechanism of poly(3-methylthiophene) has been studied employing in situ spectroelectrochemical and kinetic measurements. Results indicate that: (i) the polymer film grows only when 3-methylthiophene is oxidized, suggesting that the radical-radical coupling reaction is important for the polymer growth; (ii) concentrations of intermediate species, i.e., radical cations of the trimer and tetramer, are maintained at a steady-state level during the growth; and (iii) both monomer and polymer concentrations appear in the rate expression, indicating that both the monomer and polymer participate in the polymer growth. The growth is not autocatalytic, and oxidation of both the monomer and oligomer or polymer is required for further growth of the polymer. The reaction order in the rate expression depends on experimental conditions ranging 0.5 -1 for the monomer, while it is about 0.5 for the polymer.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 157.182.150.22 Downloaded on 2015-03-10 to IP

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Electrochemically prepared poly‐3‐methylthiophene has been characterized employing spectroelectrochemical techniques. Results indicate that both oxidized and reduced forms of the polymer are stoichiometrically stable and the doping process is chemically reversible. The anodic doping level is between 0.12∼0.19 as determined from spectroelectrochemical measurements, and several different functional groups appear to undergo redox reactions.

The oxidation of electrochemically grown poly(3-methylthiophene) and its other spectroscopic properties have been studied by in-situ spectroelectrochemlcal techniques as well as in-situ conductivity measurements, and the results are reported. An absorptivity of 1.1 X 105 cm'1 is reported for the absorption band at 490 nm for a neutral, reduced polymer film grown in propylene carbonate. The oxidation of the neutral polymer to the cation radical, or polaron, and its further oxidation to the dication, or bipolaron, are shown to take place at about 0.45 and 0.80 V, respectively, and be controlled by the diffusion of counterions. In-situ conductivity measurements of the film show that both the polaron and bipolaron are charge carriers. We conclude from the results that at least two chemically and optically different species, radical cation and dication, and perhaps other products, are produced in different potential regimes upon oxidation of poly(3-methylthiophene).