CHAIN MOBILITY AND CATION COORDINATION IN THE POLYMER ELECTROLYTES M[N(CF3SO2)(2)](2)PEON WITH M=MG, CA, SR, AND BA

The poly(ethylene oxide)-based solid electrolytes M[N(CF3SO2)(2)](2)PE On with M = Mg, Ca, Sr, and Ba and n = 6-24 have been examined with pr oton NMR spectroscopy, DSC, and X-ray diffraction to explore some of t heir dynamic and structural properties. Changes in salt concentration appear to be more important than changes in ionic radius for propertie s such as activation energies and correlation times for conformational transformations. Above the glass transition temperature, the fully am orphous samples with M = Mg and n less than or equal to 12 produce pro ton NMR spectra that can be decomposed into two components of differen t width. This is a consequence of the different dynamic properties of cation-coordinated and noncoordinated polymer chain segments. The rela tionship between the areas of these components results in a maximum ef fective coordination number for the Mg2+ ion between 6 and 7, dependin g on salt concentration. Some of the initially amorphous samples under go slow crystallization, producing aged samples with crystalline PEO-s alt complexes.