ELECTROCHEMICAL OXIDATION OF 1,4-DIALKOXYBENZENES IN ORGANIC MEDIA - REVERSIBLE ONE-ELECTRON PROCESS IN A METHYLENE CHLORIDE TRIFLUOROACETIC ACID MIXTURE AND ELECTROPOLYMERIZATION REACTION IN DRY ACETONITRILE/

1,4-Dialkoxybenzenes (from dimethoxy to didecyloxy) can be oxidized re versibly into stable radical cations in a CH2Cl2 + CF3COOH mixture con taining 0.2 M NBu4BF4. The effects of the alkoxy substituents on the s hift of the redox potentials (from the respective Taft substituent con stants) as well as the variations of diffusion coefficients D and the charge transfer rate constants k(s) are examined. In particular, the D values are found to decrease from about 1.0 X 10(-5) to 0.4 X 10(-5) cm(2) s(-1) with the lengthening of ether chains, while the k(s) value s are around 2 X 10(-2) cms(-1). In another investigation medium, such as dry CH3CN, the oxidation of 1,4-dialkoxybenzenes leads to the depo sition onto the electrode surface of the corresponding p-doped polyphe nylenes, except for the 1,4-didecyloxybenzene which does not electropo lymerize. The doping level decreases with the lengthening of ether cha ins and polymers globally exhibit poor film properties. The apparent i nstability of their electrochemical response and probably the low cond uctivity can be attributed to a powdery structure, a poor attachment o nto the electrode surface and a lack of cohesion of the deposit.