An in situ spectroelectrochemical investigation of the copolymerization ofdiaminobenzenesulfonic acid with aniline and its derivatives

In situ UV-Visible spectroelectrochemical studies on the copolymerization o f diaminobenzenesulfonic acid (DABSA) with aniline (ANI), o-toluidine (OT) and N-methyl aniline (NMA) were carried out potentiostatically in aqueous 1 .0 M H2SO4 solutions containing the mixture of monomers (DABSA and ANI/OT/N MA) at an optically transparent electrode. Copolymerization studies were pe rformed for different feed ratios of the comonomers. Polymerization of DABS A was also carried out to bring out the differences in the spectral charact eristics between homopolymerization and copolymerization. UV-Visible spectr a were recorded at various timer intervals during copolymerization and homo polymerization of DABSA. Four absorption bands were noticed for the copolym erization in contrast to the three bands for homopolymerization. The appear ance of bands at 672, 633 and 668 nm for copolymerization of DABSA with ANI , OT and NMA, respectively, are attributed to the exitonic transitions asso ciated with these monomer units in the copolymer. The exitonic band of PANI /PANI derivative units that appeared during copolymerization was markedly i nfluenced by the presence of sulfonic acid groups in the copolymer. This wa s demonstrated by observing its influence in the absence of applied potenti al and also by following the changes in the band positions through spectroe lectrochemical studies on the copolymerization of DABSA with ANI or OT or N MA. The dependences of absorbances on time at the wavelengths corresponding to polaronic and exitonic transitions of the polymers were deduced. The de crease in absorbances of the exitonic band arising from the dedoping caused by sulfonic acid groups in the polymer showed variations in the copolymeri zation of DABSA with ANI, OT and NMA. The following trend was noticed ANI > NMA > OT. (C) 2001 Elsevier Science Ltd. All rights reserved.