Pulsed field gradient n.m.r. diffusion measurements on electrolyte solutions containing LiCF 3SO 3

Abstract

The pulsed field gradient spin echo technique has been used to measure the self-diffusion coefficients of 7Li, 19F and protons in two electrolyte solutions, based on LiCF 3SO 3 in either tetraglyme or N,N-dimethylformamide, respectively. In addition, the ionic conductivities were determined by ac conductivity measurements and the viscosities with an Ostwald viscometer. Predicted values for the ionic conductivity were obtained from the n.m.r. diffusivities using the Nernst–Einstein equation and compared with those from direct measurements, to provide estimates of the degree of ionic association as a function of temperature and salt concentration. The possible correlations between solution viscosity and the self-diffusion coefficients of the ions were explored on the basis of the Stokes–Einstein equation. Finally, the results were considered in the light of previously reported Raman spectroscopy measurements and in terms of the Walden product of the molal conductivity and viscosity of the electrolyte.