FORMATION OF GRAPHITE FIBER-POLYPYRROLE COATINGS BY AQUEOUS ELECTROCHEMICAL POLYMERIZATION

The aqueous electrochemically initiated polymerization of pyrrole has been successfully performed on graphite fibres from a solution containing the monomer and toluene-4-sulfonic acid sodium salt. The effects of the initial monomer concentration, supporting electrolyte concentration and applied voltage on the rate of electropolymerization of pyrrole have been investigated in an attempt to ascertain the optimum conditions for the process. The rate of electropolymerization of pyrrole increased with the initial monomer concentration and the applied voltage up to the peak oxidation potential of pyrrole, similar to 1.5 V, beyond which a significant decrease in the rate occurred. Increasing the concentration of toluene-4-sulfonic acid sodium salt from 0.05 to 0.10 M had little impact on the rate of electropolymerization. However, a sharp increase in the rate occurred when the electrolyte concentration was raised to 0.5 M. The morphology of the electropolymerized pyrrole is highly porous and grainy. The individual single graphite fibre filament is completely covered with polypyrrole after about 30 s of electropolymerization.