COMPLEXATION OF POLYANILINE WITH LEWIS ACIDS - A MÖSSBAUER SPECTROSCOPY STUDY

Krzysztof Bieñkowski1, Jean-Louis Oddou2, Olivier Horner2, Irena Kulszewicz-Bajer1, Francoise Genoud3, Jan Suwalski4, Adam Pron3

1Faculty of Chemistry, Warsaw University of Technology, 3 Noakowskiego Str., 00-664 Warsaw, Poland,
2Laboratoire de Physicochimie des Métaux en Biologie, CEA Grenoble/DBMS, 17 des Martyrs Ave., 38054 Grenoble, France,
3Laboratoire de Physique des Métaux Synthétiques, CEA Grenoble SI3M/DRFMC, 17 des Martyrs Ave., 38054 Grenoble, France,
4Institute of Atomic Energy, 05-400 Otwock-Œwierk, Poland


Doping with Lewis acid is a new method for improving solution processibility of conductive polyaniline. We report here detailed Mössbauer spectroscopy studies of polyaniline complexed with Lewis acids containing Mössbauer active nuclei, namely SnCl4 and FeCl3. Films of Lewis acid doped polyaniline cast from nitromethane solutions show stoichiometries of PANI(MeCln)1(CH3NO2)1 (where n = 3 or 4, Me denotes Sn or Fe and PANI denotes one aniline repeat unit), which means that both types of polyaniline nitrogens (imine and amine) participate in the complexation reaction, and one solvent molecule is introduced in to the polymer matrix per one Lewis acid molecule. Mössbauer parameters of polyaniline doped with SnCl4 are consistent with hexacoordinated Sn(IV) in an environment of nonequivalent ligands. The spectrum of PANI doped with FeCl3 consists of two doublets with distinctly different Mössbauer parameters, which can be ascribed to two types of complexing sites (amine and imine nitrogens). From the temperature dependence of the isomer shift and the recoil free absorption, we have calculated the Mössbauer lattice temperature Qm as probed by both complexing sites, which are 83 K for amine and 126 K for imine sites.