ION COORDINATION AND CHAIN MOBILITY IN LA(CF3SO3)(3)PEON STUDIED WITHNMR-SPECTROSCOPY

The polymer electrolyte system La(CF3SO3)(3)PEOn has been examined wit h differential scanning calorimetry (DSC) and NMR spectroscopy in orde r to analyze some of its structural and dynamic properties. Above the glass transition temperature, the fully amorphous samples with n less than or equal to 16 give rise to H-1 NMR spectra that consist of two c omponents of different width, corresponding to different dynamic prope rties of cation-coordinated and noncoordinated polymer chain segments. For n = 9, almost all chain segments interact with the cation, result ing in an ether oxygen coordination number close to 9. This conclusion is supported by DSC measurements. For the more dilute samples with n = 12 and n = 16, the NMR data result in a strongly temperature depende nt effective coordination number. The changes in coordination number w ith temperature are explained in terms of polymer chain conformation, on the basis of an earlier IR spectroscopy study. As a consequence of the La3+ ion's strong ability to coordinate the polymer chain, the cha in mobility is severely restricted and the ionic conductivity low, eve n in totally amorphous samples.