Structural studies of halogen-substituted polyanilines by X-ray photoelectron spectroscopy

Abstract

The intrinsic oxidation states, the imine/amine ratios in particular, of the halogen monosubstituted polyanilines prepared by the oxidative chemical polymerization in HCl and H2SO4 media were determined quantitatively by X-ray photoelectron spectroscopy (XPS). Neither the type of halogen substituent (Cl, Br and I), nor the position of substitution, nor the protonic acid media caused a significant variation in the intrinsic oxidation states of the resulting polymers. The N 1s core-level spectra revealed an imine/amine ratio of 0.5:1 or less in all of the polymer bases. The position of substitution caused a wide variation in the polymer yield, with 2-substituted aniline giving the highest yield. Protonation by H2SO4 gave rise to monovalent sulfate anions and nitrogenonium cations. However, 'protonation' by HCl resulted only in covalently bonded chlorine, with most of the imine nitrogens remaining unprotonated. © 1990.