ELECTROGENERATION - A FAST WAY, THROUGH A COMPLEX MECHANISM, TO OBTAIN POLYCONJUGATED TAILORED MATERIALS

Polypyrrole was electrogenerated, by potential steps, from acetonitrile, water, and acetonitrile/water mixtures, using a platinum disk electrode. The amount of polymer grafted onto the electrode was followed indirectly, via the evolution of the storage charge obtained from a control voltammogram of the polymer film in the background solution. The ratio between the storage charge and the polymerization charge provides the 'charge-storage efficiency', which is a measurement of the redox properties of the polymer film. These efficiencies change with the percentage of water added to the organic media, showing the change in the electropolymerization mechanism with the water/acetonitrile ratio. Thus, the films having the better charge-storage ability are those synthesized in acetonitrile with a 1% water content. On the other hand, polythiophene films were electrogenerated at 1700 mV, over various polarization times, from 0.05 and 0.25 M thiophene-acetonitrile solutions. In this case, the charge-storage efficiency was calculated from the ratio between the storage charge and the polymer weight. The storage efficiency increases with polarization time and increases with the monomer concentration for films of similar thickness. This behaviour has been interpreted from the discharge of the organic solvent's residual water in competition with the monomer discharge.