The oxidative polymerization of N-(4-aminophenyl)aniline (AD) to the conducting emeraldine salt (2.6 x 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 O-2 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 O-2 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). (C) 2009 Elsevier Inc. All rights reserved.