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. Th e gel consisted of poly(methyl methacrylate) complexed with a liquid electr olyte of lithium perchlorate salt in an ethylene carbonate and propylene ca rbonate solution. The mole ratio composition was determined throughout the sample by means of Raman spectroscopy, which reveal a gradual vertical decr ease of the polymer concentration. The photon correlation experiments show three dynamical processes of which two are attributed to diffusive processe s, related to the solvent, and one to segmental motion, due to the relaxati on of the polymer matrix. As the polymer concentration is increased the fas t diffusive process gets slower, while there is no or a very small effect o n the segmental motion. The implications for the overall performance in app lications concerning ionic conductivity is also briefly discussed. (C) 2000 Elsevier Science B.V. All rights reserved.