PHYSICAL AND SPECTROSCOPIC STUDIES OF POLYPYRROLE FILMS CONTAINING TETRASULFONATED METALLOPHTHALOCYANINE COUNTERIONS PREPARED FROM NONAQUEOUS SOLUTION

A range of polypyrrole films containing tetrasulfonated metallophthalocyanines (PPyMPcTs, M = Co and Fe) as counterions, prepared electrochemically from propylene carbonate solution, have been characterized in detail. The room-temperature conductivity values (0.1-0.8 S/cm) are lower than those determined on the well known p-toluenesulfonate system, PPyPTS (20-80 S/cm), prepared here under similar conditions, and this is due, in part, to the difference in size of the counterions. The conductivity of PPyPTS, a form of polypyrrole normally regarded as environmentally stable, was shown to be sensitive toward atmospheric oxygen and water. The conductivity of PPyMPcTs films decreased even more rapidly due to destructive oxidation by oxygen plus the effects of water vapor. By using a competitively doped film PPyCoPcTs/PTS, it was shown that part of the conductivity decrease in PPyCoPcTs was actually reversible and associated with the uptake of water vapor. In attempting to discover the reasons for conductivity differences and stability differences in these films, it was found that the morphology of growth surfaces of PPyMPcTs (M = Co, Fe, and Ni), as viewed by scanning electron microscopy, was dependent on the nature of M. The morphology of the anode surface of PPyCoPcTs was also quite different from that normally reported for films of PPy. Spectroscopic techniques, some of which (EPR and Mossbauer) have been rarely used to probe the counterions of PPy, show subtle phenomena such as the presence of both aggregated and monomeric forms of CoPcTs within PPyCoPcTs, the monomeric form being strongly electrostatically coupled to the cationic polymer. Mossbauer effect studies on PPyFePcTs indicated the coexistence of a high-spin Fe(II) species as well as various spin states of Fe(III). Previous reports of this system have clearly underestimated its molecular complexity.