Diffusive and segmental dynamics in polymer gel electrolytes

Dynamic light scattering data on a polymer gel electrolyte with a complex r elaxation behavior is presented. The electrolyte consists of lithium perchl orate dissolved in an ethylene carbonate and propylene carbonate solution t hat is immobilized with poly(methyl methacrylate). We attribute the observe d relaxation processes to two diffusive and one segmental relaxation proces ses based on the form of the time decay of the intermediate scattering func tion and the corresponding temperature and wave vector dependencies. The dy namic light scattering results are compared with the ionic conductivity, wh ich reveals a close connection between the fast diffusive motion of the low molecular weight solvent within the gel and the ionic conductivity. This m otion is strongly decoupled from and considerably faster than the segmental motion of the polymer matrix. The results indicate that the ionic transpor t occurs mainly within the low molecular weight solvent. (C) 1999 American Institute of Physics. [S0021-9606(99)50248-1].