A green route to conducting polyaniline by copper catalysis

The oxidative polymerization of N-(4-aminophenyl)aniline (AD) to the conducting emeraldine salt (2.6 × 10-2 S cm-1) has been investigated using dioxygen or hydrogen peroxide as the oxidant in aqueous solution under mild conditions. The spontaneous oxidation by O2 takes place with a modest yield (13%) while H2O2 allows a better result (43% yield). On adding acetonitrile as a co-solvent, the polymerization is completely suppressed with both the reagents. A strong catalytic effect has been detected by using Cu, CuCl, and CuCl2, being all these simple copper compounds similarly efficient using either O2 or H2O2 reagents, thus allowing yields up to 86-93% of emeraldine. The poisoning effect of acetonitrile has been observed also in the case of the copper-catalyzed reactions but with a minor impact (5-14% decrement).