X-ray photoelectron spectroscopic studies of charge transfer interactions in electroactive polyaniline

Abstract

Four modes of charge transfer interactions in polyaniline (PAN), viz. acid protonation, self-doping, charge transfer interactions with organic acceptors, and charge transfer interactions with surface grafted functional polymers have been studied by X-ray photoelectron spectroscopy (XPS). In the case of acid protonation, the protonation behavior of volatile and non-volatile acid differs. The structures of sulfonated leucomeraldine (LM) and nigraniline (NA) are similar to those of sulfonated and self-protonated emeraldine (EM). A substantially higher degree of charge transfer interaction with the organic acceptors is observed for EM film that has been subjected to one cycle of acid/base treatment. The charge transfer interactions with the organic acceptors have proceeded further than the pure formation of molecular complexes. Both pristine and Ar plasma or O3 pretreated EM films are susceptible to surface modifications by graft copolymerization. The protonic acid functional groups of the graft readily give rise to a self-protonated EM surface.