The results of a spectroscopic and thermal study of high molecular weight (PEO)(n)NH4SO3CF3 (n = 1-80) complexes are presented. Infrared spectroscopy shows a shift and splitting of the N-H stretching mode at high salt concentrations, indicating the interaction of NH4+ ions with the ether oxygen atoms of the polymer backbone. Combined spectroscopic and differential scanning calorimetric (DSC) studies confirm previously reported compound formation at ether oxygen:cation ratios of 8:1 and 4:1. These studies also indicate the formation of a 1:1 compound. The ionic conductivity of the 1:1 compound shows unusual temperature-dependent behavior, suggestive of a X-transition.