Application of FTIR spectroscopy for structural characterization of ternary poly(acrylic acid)-metal-poly(vinyl pyrrolidone) complexes

The FTIR spectroscopic technique was used in the study of ternary polymer-metal complexes containing two polyelectrolytes of opposite charge and metal ions. The structure of the ternary (PAA-Fe3+-pVp) complexes was examined by following the changes in their infrared spectra. It was found that the shapes of the absorption bands of the resultant compounds are influenced by the presence of Fe3+. According to this result it was suggested that two types of structure which differ in the composition are formed, one of which results from the coordination of Fe3+ with PAA-PVP complex and the other is due to the formation of Fe3+ polycarboxylate. Comparison between the spectrum of PAA-PVP complex and those of the compounds resulted from the reaction between the two opposite charged electrolytes, PAA and PVP and each of the divalent metal chlorides NiCl2, CoCl2, CuCl2, and ZnCl2) led to the conclusion that a reaction took place between the divalent transition metal chlorides and the extent of reaction depends on the nature of metal ions and PAA- PVP complex. The FTIR spectra of the precipitate resulted from the mixtures of PAA-PVP and Ni(NO3)(2) or Sr(NO3)(2) were investigated. It was noted that the addition of Ni(NO3)(2) or Sr(NO3)(2) to the mixture of the electrolytes of PAA and PVP provoked appreciable changes in the characteristic spectral features of the complex resulting from the interaction of the metal ions with the polymer-polymer complex. The FTIR spectra of the precipitate resulted from the reaction between CeCl3, ErCl3, and LaCl3 were also investigated. It was concluded that a reaction took place between the rare earth metals and the PPC. This means that ternary polymer-metal-polymer complexes were formed. The extent of changes in the spectral features differs from metal to metal according to the nature of metal ions. (c) 2007 Wiley Periodicals, Inc.