ELECTROOXIDATIVE DEPOSITION OF POLYPYRROLE AND POLYANILINE ON SELF-ASSEMBLED MONOLAYER MODIFIED ELECTRODES

Self-assembled monolayers (SAMs) of omega-substituted alkanethiols on gold display different effects on the kinetics of electrochemical depo sition of polypyrrole and polyaniline. Hydrophobic monolayers of dodec anethiol and octadecanethiol initially retard the deposition of polypy rrole. However, as soon as polymerization is nucleated, a rough polyme r film is rapidly deposited. Monolayers of 12-amino-1-dodecanethiol, w hich are protonated under the acidic conditions required for polyanili ne deposition, provide a good barrier to aniline oxidation. The respon se of SAM-modified electrodes to (N,N-(dimethylamino)methyl)ferrocene in acidic solution follows similar trends observed for the blocking of aniline oxidation. Thus, the Coulombic repulsion between the protonat ed monolayer and the diffusing anilinium monomer appears important in providing a barrier to the electrooxidative deposition of polyaniline.