Cation environment in polyether complexes based on poly (tetramethylene glycol) doped with zinc and cobalt chlorides

X-ray absorption spectroscopy [extended X-ray absorption fine structure (EX AFS) and X-ray absorption near-edge structure (XANTES)], differential scann ing calorimetry, and Raman spectroscopy measurements were performed for a s eries of liquid polyether/salt systems prepared with poly(tetramethylene gl ycol) (PTMG) and the copolymer poly(tetramethylene glycol-co-ethylene glyco l) as matrices and zinc and cobalt chlorides as dopants in the concentratio n range of n = 30-90, where n is the molar ratio of oxygen to metal cation. According to EXAFS, XANES, and Raman results, even in diluted solutions, t hese complexes exist mostly as undissociated ZnCl2 and CoCl2 species, prese nting a weak cation-polymer interaction. EXAFS results indicate that for po lymer/ZnCl2 systems, the nearest metal neighbors are only chlorine atoms. H owever, for polymer/CoCl2 samples, oxygen is also observed coordinating the metal. Raman spectra do not support any feature related specifically to th e cation-polymer interaction. Nevertheless, for both salts the symmetric st retching vibrations are located in frequencies characteristic of salt in so lution, which means that the polymer solvating action is effective. Differe ntial scanning calorimetry data show an increase in the glass-transition te mperature for all polymer/salt systems in relation to the pure polymer samp les, a consequence of the increase in the macromolecular chain stiffening p roduced by the presence of the salt. This result corroborates the existence of polymer-salt interactions. (C) 2001 John Wiley & Sons, Inc.