Surface studies of chemically processed polyaniline films

Abstract

Surface structures and redox states of pristine, protonated and surface modified emeraldine (EM) films have been studied by angle-dependent X-ray photoelectron spectroscopy (XPS). The first protonation-deprotonation cycle can increase the intrinsic oxidation state (imine/ amine ratio) of EM to near that of pernigraniline. The outermost surface of the EM film generally has a significantly lower intrinsic oxidation state than the bulk. In contrast to protonation by volatile acids, the outermost surface of EM film protonated by a non-volatile acid can exhibit a significantly higher protonation level and almost all the amine nitrogens, in addition to the imine nitrogens, are susceptible to protonation. The pristine, O3-pretreated and once-cycled (acid-base) EM films also exhibit distinctive behaviour towards surface modifications by near-UV light induced graft copolymerization with hydrophilic polymers. The surface characteristics, including morphology, of the three types of films after grafting are also reported. © 1993.