Polymer concentration dependence of the dynamics in gel electrolytes

A polymer gel electrolyte sample with a gradually varying concentration of polymer have been examined by Raman and photon correlation spectroscopy. The gel consisted of poly(methyl methacrylate) complexed with a liquid electrolyte of lithium perchlorate salt in an ethylene carbonate and propylene carbonate solution. The mole ratio composition was determined throughout the sample by means of Raman spectroscopy, which reveal a gradual vertical decrease of the polymer concentration. The photon correlation experiments show three dynamical processes of which two are attributed to diffusive processes, related to the solvent, and one to segmental motion, due to the relaxation of the polymer matrix. As the polymer concentration is increased the fast diffusive process gets slower, while there is no or a very small effect on the segmental motion. The implications for the overall performance in applications concerning ionic conductivity is also briefly discussed.