PHYSICAL AND SPECTROSCOPIC STUDIES OF POLYPYRROLE FILMS CONTAINING TRANSITION-METAL EDTA CHELATES

Polypyrrole films containing transition-metal chelate counteranions, based on ethylenediaminetetraacetate (EDTA4-) and cyclohexanediaminetetraacetate (CDTA4-), have been prepared. The polymers (PPyMEDTA (M = Co, Cr, and Fe) and PPyMCDTA (M = Co and Fe)) have been characterized by elemental analysis, conductivity, X-ray diffraction, and TEM studies, as well as infrared, UV-visible, EPR, and Mossbauer spectroscopy. The conductivity of PPyFeEDTA and PPyCrEDTA initially increased upon exposure to the environment and then stabilized, while that of PPyCoEDTA initially increased and then decreased very slowly; this behavior is superior to that of the well-known p-toluenesulfonate system (PPyPTS). The conductivity, degree of order, and conjugation length of the polymers were dependent upon the nature of the incorporated counteranion. TEM investigations of thin films of PPyCoEDTA revealed some crystallinity, lattice fringes being observed. EPR spectroscopy showed that the coordination of EDTA4- within the counteranion of PPyCrEDTA was sexadentate. The low-temperature Mossbauer spectrum of PPyFeEDTA exhibited magnetic structure and indicated the presence of at least two counteranion environments. In addition to an aggregated form, a large proportion of the counteranions is well dispersed within the polymer matrix.