Polyaniline: Synthesis and properties of pernigraniline base

Abstract

The most highly oxidized polyaniline, in the form of pernigraniline base, can be synthesized as an analytically and oxidatively pure solid (powder or large free-standing films) by the controlled oxidation of emeraldine base by m-chloroperbenzoic acid or directly from aniline by oxidative polymerization with (NH4)2S2O8. In the first method, the emeraldine oxidation state is converted directly to the pernigraniline oxidation state without passing through any intermediate discrete oxidation state at the molecular level. Treatment of perigraniline base with aqueous HCl results not in a protonated form of pernigraniline but in reductive ring chlorination to give the emeraldine oxidation state.