CHEMICAL PREPARATION OF POLYANILINE CONTAINING HETEROPOLYANIONS

Polyaniline containing anions of phosphotungstic acid has been prepared in a one-step reaction involving oxidation of aniline with ammonium persulfate in the presence of phosphotungstic acid. The presence of heteropolyanions (so-called structural Keggin units) in the polymer has been confirmed by elemental analysis and IR spectroscopy which showed the existence of the five strongest modes of the inserted anion in addition to the features characteristic of the protonated polyaniline chain. The anions enter the polymer matrix in their highest oxidation state (all tungstens at +6 oxidation level) since EPR spectra show only one single line characteristic of the polyaniline radical with no lines attributable to the reduced form of tungsten. The obtained product seems to be an excellent candidate for application in heterogeneous catalysis involving acid-base processes because, despite the fact that it deteriorates electrically at elevated temperatures, it retains catalytically active Keggin units.