Interplay between the Structure and Relaxations in Selemion AMV Hydroxide Conducting Membranes for AEMFC Applications

Selemion AMV was studied to examine the relationship between the membrane chemical structure and its properties. The structure of AMV consists of two components: the functionalized polystyrene copolymer containing the ion-exchange moieties and PVC which is likely blended with copolymer. The PVC is primarily responsible for the mechanical properties of the membrane, but seems to undergo degradation during the anion-exchange process that leads to a reduction of the storage modulus. The functionalized polystyrene copolymer with the ion-exchange groups is primarily responsible for the electrical properties of the membrane. The AMV and AMVOH membranes exhibited conductivities of 2 and 7 mS·cm-1 at 25°C, respectively. The membrane exhibited Arrhenius behavior in all conditions that suggests the dynamics of the membrane are not significantly involved in the mechanism of long-range conduction. The MVOH membrane has two predominant pathways of charge exchange through the membrane: one through the bulk of the hydrophilic domains that is associated with the electrode polarization and another along the interface between the hydrophobic and hydrophilic domains associated with the interfacial polarization. These two separate phenomena provide significant percolation pathways that merge into a single contribution to the long-range charge migration at high water content. However, conduction along the interface does not provide as important a contribution to the long-range conductivity in the chloride form of the membrane.