Influence of the Degree of Sulfonation on the Structure and Dynamics of Sulfonated Polystyrene Copolymers

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−Fröhlich 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.