Development of Modulation–Excitation Synchrotron Small-Angle X-Ray Scattering with Subnanometer Resolution

The development of advanced analytical techniques is crucial for the detailed nanoscale characterization of materials. This study introduces a novel approach, modulation-excitation synchrotron small-angle X-ray scattering (ME-SAXS). By integrating a modulation-excitation method with synchrotron-based SAXS, we achieved enhanced sensitivity and resolution in detecting dynamic structural changes and determining their kinetics. To the best of our knowledge, this is the first application of modulation-excitation to SAXS. We selected Nafion films─sulfonated tetrafluoroethylene-based membranes─under repeated cycles of gas-phase hydration and dehydration as a model system to showcase the power of ME-SAXS. This technique provided insights into the morphology of the polymeric system components (matrix knee crystallites and ionomer channels) under hydration at different temperatures and film thicknesses. The application of ME-SAXS to Nafion films demonstrates its potential in revealing intricate changes with subnanometer resolution, paving the way for future advancements beyond polymer science to other fields of materials science and engineering.