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We use 2H NMR stimulated-echo spectroscopy to measure two-time correlationfunctions characterizing the polymer segmental motion in polymer electrolytesPPO-LiClO4 near the glass transition temperature Tg. To investigate effects ofthe salt on the polymer dynamics, we compare results for different ether oxygento lithium ratios, namely, 6:1, 15:1, 30:1 and infinity. For all compositions,we find nonexponential correlation functions, which can be described by aKohlrausch function. The mean correlation times show quantitatively that anincrease of the salt concentration results in a strong slowing down of thesegmental motion. Consistently, for the high 6:1 salt concentration, a highapparent activation energy E_a=4.1eV characterizes the temperature dependenceof the mean correlation times at Tg < T< 1.1T_g, while smaller values E_a=2.5eVare observed for moderate salt contents. The correlation functions are mostnonexponential for 15:1 PPO-LiClO4, whereas the stretching is reduced forhigher and lower salt concentrations. A similar dependence of the correlationfunctions on the evolution time in the presence and in the absence of ionsindicates that addition of salt hardly affects the reorientational mechanism.For all compositions, mean jump angles of about 15 degree characterize thesegmental reorientation. In addition, comparison of results from 2H and 7Li NMRstimulated-echo experiments suggests a coupling of ion and polymer dynamics in15:1 PPO-LiClO4.Comment: 14 pages, 12 figure

Ion and polymer dynamics in polymer electrolytes PPO–LiClO4.II. H2 and Li7 NMR stimulated-echo experiments