TEMPERATURE-DEPENDENCE OF ION-PAIRING OF A POTASSIUM-SALT IN NONAQUEOUS LIQUID AND POLYMER ELECTROLYTES - X-RAY-ABSORPTION STUDIES

Near-edge x-ray absorption fine structure spectroscopy was used to stu dy the effect of temperature on ion pairing of a potassium salt in a m odified carbonate (MC3) solution and in a poly(ethylene oxide)-potassi um salt complex that used MC3 as a plasticizer. The modified carbonate was made by attaching three ethylene oxide units to the four position of ethylene carbonate. Spectra were obtained, at the K edge of potass ium, over the temperature range of 25-110 degrees C. Studies of refere nce systems showed a correlation between ion pairing and white line sp litting in the near-edge region of the spectra. The degree of white li ne splitting was used as a qualitative indicator of the degree of ion pairing as a function of temperature. The results indicate that, in bo th systems, the number of ion pairs increases with increasing temperat ure.