Surface-catalyzed growth of poly(2-methoxyaniline) on gold

We report on catalytic growth of poly(2-methoxyaniline) on gold surface by in situ polymerization. The mechanism of catalysis and products of monomer oxidation are elucidated on the basis of complementary investigations including Raman and UV–Vis spectroscopy, surface plasmon resonance, electrospray ionization mass spectrometry, gel permeation chromatography as well as electrochemical and microscopic techniques. It was shown that chemical oxidation of 2-methoxyaniline in acidic medium results in formation of a linear trimer which is the only stable product yielded in the bulk of the solution. However, introduction of a gold substrate into the reaction mixture induces polymerization of monomers/oligomers and formation of a thin polymeric film on the surface. This catalytic activity of gold is associated with adsorption of trimeric species onto the metal. The oligomers, being in fully oxidized (quinoid) form in the solution, are reduced to radical cations after adsorption onto the gold substrate. Since the radical cations are significantly more reactive than fully oxidized species, the polymerization proceeds on the surface, while it is inhibited in the solution.