Figure shows the electrolyte uptake and area swelling of the STz25 and STz30 membranes equilibrated in aqueous KOH with concentrations ranging from 5 to 25 wt%. In general, the trend observed for electrolyte uptake was a decrease in uptake with an increasing concentration of the surrounding KOH solution. For STz25, the electrolyte uptake decreased from 110% in 5 wt% KOH to 53% when the KOH concentration was increased to 25 wt%. The electrolyte uptake was slightly lower in 20% KOH, which is likely a result of experimental uncertainty rather than a local minimum. The STz30 membrane exhibited a similar behavior, but with significantly higher uptakes due to the higher tetrazole content. The electrolyte uptake of STz30 decreased from 362% to 118% as the KOH concentration increased from 10 to 25 wt%.