Dynamics of sulfonated polystyrene copolymers using broadband dielectric spectroscopy

We examine the dynamics of acid and methylated precursors to sulfonated polystyrene ionomers. Dielectric relaxation spectroscopy was the primary tool used in the investigation of the dynamics, and dynamic mechanical analysis, Fourier transform infrared spectroscopy, and differential scanning calorimetry were employed in a complementary role. Monodisperse polystyrene was sulfonated to 1 and 7 mol % and the behavior compared to that of neat polystyrene and methyl-sulfonated polystyrene. Three relaxations were identified in dielectric spectra of the acid form of the sulfonated polystyrenes: the segmental alpha process, a relaxation arising from the presence of hydrogen bonds (alpha*), and a local beta process. The alpha* process followed Arrhenius behavior, and its relaxation strength decreased significantly with increasing temperature, indicating that the strength is related to the number of associating complexes, which decreases with increasing temperature. A qualitatively similar trend is observed in the infrared absorption indicative of hydrogen bonding over the same temperature range.