A Raman, ac impedance and pfg-NMR investigation of poly(ethylene oxide) dimethyl ether (400) complexed with LiCF3SO3

ac impedance, Raman spectroscopy and pulsed field gradient NMR measurements have been conducted on solutions of poly(ethylene oxide), dimethyl ether of molecular weight 400 complexed, with LiCF3SO3 as a function of salt concentration; the ether oxygen to alkali metal cation ratios (O:M) ranging from 53:1 to 563:1. From an analysis of the nu(s)(SO3) band envelope of the triflate anion, the relative concentrations of anions in various chemical environments have been calculated. A slight redissociation effect is observed with increasing salt concentration which correlates well with an observed increase in the molar conductivity. Pulsed field gradient NMR measurements show that the H-1, Li-7 and F-19 self-diffusion coefficients all decrease monotonically with increasing salt concentration. Experimental conductivity data is compared to values calculated from the diffusion coefficients using the Nernst-Einstein relation. We find that the calculated values are higher for all concentrations; the discrepancy increases with decreasing salt concentration. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.