Short-Side-Chain Perfluorosulfonic Acid Ionomer Dispersions in N-Propanol/Water: From Nanostructures to Viscosity

The multiscale structural organization of a short-side-chain perfluorosulfonic acid (SSC PFSA) ionomer in N-propanol/water mixtures was elucidated through a combination of small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), and rheological analysis to clarify its influence on catalyst ink processability for proton exchange membrane fuel cells. SAXS revealed solvent-dependent aggregate structures and polyelectrolyte-like behavior, while DLS tracked the evolution of agglomerate size upon aging. Cryo-TEM provided direct visualization of aggregate and agglomerate morphologies, supporting the findings from scattering techniques. Rheological measurements demonstrated that viscosity increases correlate with agglomerate growth and solvent composition, identifying distinct concentration regimes. These combined results enhance understanding of the relationship between ionomer structuring and rheological properties and offer new insights for optimizing ink formulations and catalyst layer quality.