Catalytic effects of selected transition metal ions in the synthesis of lignosulfonic acid doped polyaniline

Lignosulfonic acid doped polyaniline (LIGNO-PANI) is a water-dispersible conducting polymer. The incorporation of dopants to achieve higher conductivities in addition to lignosulfonates during the polymerization process results in prohibitively long initiation times. A variety of transition metal ions including silver and ferrous ions were studied as potential catalysts for the reaction. Silver nitrate was found to have superior catalytic properties followed closely by ferrous sulfate heptahydrate. The effects of these ions on the synthesis of LIGNO-PANI with methanesulfonic acid (HMSA) as an additional dopant (MSA-LP) and on the synthesis of MSA-PANI were studied via potential profile monitoring. The LIGNO-PANI derivatives produced by the catalyzed reaction demonstrated no negative effects on the conductivity (10-15 S/cm) or dispersibility. In addition, residual metal analysis indicated that, although not much iron remained (< 0.01%) in the product, a large amount of silver was present (1.8%) in the final product. X-ray diffraction analysis was used to determine the identity of the silver containing moieties in the products. (c) 2005 Wiley Periodicals, Inc.