Self-diffusion of water and fluorine ions in anion-exchange polymeric materials (membranes and resin) as determined by pulsed-field gradient nuclear magnetic resonance spectroscopy

Abstract

The self-diffusion of water, ethanol and fluorine ions was studied by means of pulsed-field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy in anion-exchange materials such as membranes and a resin containing quaternary amines as functional groups. Measurements were carried out with a NMR spectrometer at a frequency of 100 MHz for 1H and 94.3 MHz for 19F. The temperature dependence of the diffusion decay components in F − form membranes equilibrated with water or an aqueous solution of NH 4F×HF was studied. The morphology of the transport channels in these materials and relationship between the structure of the membrane transport channels and self-diffusion of water and F − ions have been discussed. It was shown that the values of self-diffusion of fluorine ions in the membranes as determined by PFG-NMR are in good agreement with those obtained by means of electroconductivity measurements.