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 measure ments have been conducted on solutions of poly(ethylene oxide), dimeth yl ether of molecular weight 400 complexed, with LiCF3SO3 as a functio n of salt concentration; the ether oxygen to alkali metal cation ratio s (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 a nions in various chemical environments have been calculated. A slight redissociation effect is observed with increasing salt concentration w hich correlates well with an observed increase in the molar conductivi ty. Pulsed field gradient NMR measurements show that the H-1, Li-7 and F-19 self-diffusion coefficients all decrease monotonically with incr easing 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 a ll concentrations; the discrepancy increases with decreasing salt conc entration. (C) 1998 Published by Elsevier Science Ltd. All rights rese rved.