Resistance Measurements for Multilayer Supported Membranes

In cell, through plane resistance is an important quantity for proper characterization of multilayer supported composite membranes. Through plane resistance of a supported composite membrane is impacted by the addition of a non-conductive supporting material, effectively decreasing the density of acid sites in the composite layer. Additionally, there could be other impacts on through plane resistance due to phenomena such as changes in water transport resulting in localized lambda variation as well as possible tortuosity effects due to the support. It is possible to characterize, separately, the through plane resistance of the neat ionomer skin layers as well as the ionomer filled support composite layer by measuring the through plane resistance for a series of supported membranes varying only in ionomer skin thickness. The conductivity of the composite layer can then be compared to the conductivity of the neat ionomer, allowing for the determination of a "conductivity restriction" factor. This conductivity restriction factor can then be compared to the volume fraction of nonconductive support material in the composite layer to determine whether the impact on conductivity is due solely to acid site dilution or if there are additional losses. This analysis can be used to compare various support materials for their impact on through plane resistance. The results of this work will help guide the choice of support materials to optimize mechanical properties while minimizing the impact on through plane resistance.