Polymer fuel-cell membranes are the core component of fuel-cells having multiple functionalities including water absorption, ionic conductivity, and mechanical support. All these functionalities are correlated via the membrane nanostructure and chemical properties. This study aims at investigating the changes in the structure-uptake relationship due to membrane degradation and ageing. We show that, after in-situ chemical degradation (i.e., OCV holds), the membrane's water uptake and water-domain spacing both decrease compared to a fresh membrane. In addition, the MEA manufacturing process is also found to alter the membrane's nanostructure and uptake behavior, which suggests that changes in the properties of bare membranes during processing and cell operation must be accounted for when analyzing and modeling cell performance. The experimental data is evaluated using an energy-balance approach to examine the correlations among domain spacing, water content, and mechanical properties for degraded membranes.