Dynamics and spatial distribution of water in Nafion 117 membrane investigated by NMR spin-spin relaxation

Abstract

The dynamics and spatial distribution of water molecules in Nafion 117 membrane has been investigated by 1 H NMR. To this end, 1D and 2D spin-spin (T 2 ) relaxometry experiments were carried out as a function of the relative humidity ranging from 9 to 100%. The inverse Laplace transform was successfully applied to obtain the 1D T 2 distributions and 2D relaxation maps. The 1D T 2 distributions show two peaks at low RH and mainly one at high water content, which can be associated with the rearrangement of the exchange sites inside the polymeric channels with the amount of water. From the T 2 distribution at 70% RH three types of water were identified corresponding to different degree of molecular mobility. The 2D T 2 -T 2 maps show molecular exchange between the two water populations found at low RH, while at 70% the exchange between only the two more mobile water populations takes place.