SURFACE PRETREATMENT FOR ELECTROCHEMICAL FABRICATION OF ULTRATHIN PATTERNED CONDUCTING POLYMERS

Polypyrrole grows effectively along the glass substrates pretreated with n-alkylsilane reagents in electropolymerization from aqueous solutions, resulting in the formation of an ultrathin polypyrrole film at twin-microband electrodes. However, no effective promotion of lateral growth of polypyrrole was observed when the substrate was pretreated with 3-aminopropyltriethoxysilane or when the electrolysis was conducted in acetonitrile, suggesting that the hydrophobicity of the substrate is essential for promotion of the lateral growth of polypyrrole. The promotion effect is accounted for by adsorption of pyrrole monomers and selective deposition of intermediate oligomers at the hydrophobic surfaces. The polymerization anisotropy (the ratio of lateral growth rate to vertical growth rate) was ca. 25. The partial pretreatment provided a way of micropatterning with polypyrrole on an insulating substrate. Such a promotion effect at hydrophobic surfaces is amplified in the presence of a small amount of an anionic surfactant. Polyaniline also grows effectively along the hydrophobic surface with the polymerization anisotropy of >100.