Polyaniline with high intrinsic oxidation state

Abstract

Polyaniline (PAN) samples of high intrinsic oxidation states, such as the nigraniline (NA) and pernigraniline (PNA) oxidation states, were prepared by chemical oxidation of the 50% oxidized emeraldine (EM) base and the fully reduced leucoemeraldine (LM) base, according to the methods reported in the recent literature. X-ray photoelectron spectroscopy (XPS) was used as a primary tool for the quantitative analysis of the benzenoid amine, quinonoid imine and positively charged nitrogens corresponding to any particular intrinsic oxidation state and protonation level of the polymer. The use of iodine and ammonium persulfate as oxidants can lead to structural alterations, such as halogen addition in the former and over-oxidation and degradation in the latter. Less structural changes are observed in the m-chloroperoxybenzoic acid-oxidized material. In all the cases studied, XPS results indicate that only the 75%-oxidized NA base has been obtained in the dry state. The fully oxidized PNA probably exists in the m-chloroperoxybenzoic acid-oxidized material before drying, as suggested by optical absorption spectroscopy. The charge transfer interactions of the NA powders and films with dopants in aqueous and non-aqueous media were also investigated briefly.