Aniline oligomers versus polyaniline

This paper deals with aniline oligomers produced by the oxidation of aniline with ammonium peroxydisulfate under alkaline conditions. Oligomers obtained in 1 mol L-1 ammonium hydroxide as microspheres have been analyzed. They are brown, non-conducting, and are composed of tens of aniline constitutional units. They contain oxygen in semiquinonoid and quinonoid constitutional units or both, and sulfur in sulfonic or sulfate groups. Phenazine-like units in the oligomers have been identified by UV-visible spectra and the IR spectra support them. IR spectroscopic analysis of fractions insoluble and soluble in chloroform suggests that aniline oligomers are not uniform and strong hydrogen bonding occurs in their structure. Aniline oligomers will be potentially useful in applications that do not require conductivity but use the redox or salt-base transitions typical of polyaniline. Their applicability is illustrated by the ability to reduce silver cations to silver, base-salt transitions and in the carbonization to nitrogen-containing carbons. (C) 2011 Society of Chemical Industry