The structure and dynamics of sulfonated polystyrene (SPS) acid copolymers were investigated using X ray scattering and broadband dielectric relaxation spectroscopy (DRS) Evidence of acid group aggregation was found at 3 5, 6 7, and 9 5 mol% sulfonation An Increase in the segmental relaxation time and dielectric relaxation strength was observed with increasing acid content The average state of dipolar interactions was quantified as a function of temperature using the Onsager equation and the Kirkwood-Frohlich correlation factor Two high-temperature relaxation processes at frequencies 4-7 decades below the segmental relaxation were identified and are proposed to originate from Maxwell-Wagner-Sillars interfacial polarization and association dynamics of various assemblies of acid groups