Proton Conductivity and Partial Molar Volume of Different Polymer Electrolyte Membranes

Density and water uptake were measured for a series of 3M ionomer membranes with different acid groups and equivalent weight (ew). We have developed a systematic method for measuring the density of hydrated membranes and assessed its statistics. In gas pycnometry, a pressure change is measured upon inserting a sample into a calibrated volume of gas. The density of several perfluorosulfonic acid (PFSA) membranes was measured as a function of water content. We also calculate the partial molar volume of water in different polymer electrolytes from the density data. The partial molar volume of water and polymer components is reported for several membranes, including 3M's perfluoroimide acid (PFIA), ortho bis-acid and perfluorosulfonic acid (PFSA) with different equivalent weights.