(589a) Transport in Polymer Electrolytes for Fuel Cells: Physical Chemistry

The transport of water and protons in proton-conducting polymer membranes is a topic of major import for their application in fuel cells. Recent work has shown that certain types of interactions and structures in composite and phase-separated membranes contribute to enhanced conductivity with relatively little water present. To further understand this phenomenon, the thermodynamics and mobility of water present in such membranes have been studied. Thermal analysis has been deployed to assess the energetics of water uptake by these materials. NMR relaxation and diffusion measurements have been used in several different ways to access information. Comparison of mobility at different length scales associated with relaxation and diffusion measurements allows us to separate tortuosity and chemical interaction effects. Dilution of 1H nuclei with 2H allow us to assess the intermolecular dipolar interactions amongst water molecules, giving us clues to water structure. Finally, these data are interpreted in light of morphological aspects of the polymers and composite.