Physical Properties of Sodium Poly(styrene sulfonate): Comparison to Incompletely Sulfonated Polystyrene

Selected solution and bulk properties were measured for perfectly para-sulfonated sodium poly(styrene sulfonate) (NaP4SS) and commercially obtained poly(styrene sulfonate) (NaPSS). NaP4SS was made by the controlled radical polymerization of 4-styrene sulfonate monomer, whereas the commercially obtained NaPSS (C-NaPSS) was made from the post-treatment of polystyrene. A discrepancy in the degree of sulfonation was determined by 1H NMR, 13C NMR, and Fourier transform infrared spectroscopy (FT-IR), which showed that C-NaPSS samples had degrees of sulfonation of 89–95%. Conformation plots obtained by size exclusion chromatography coupled with multiangle light scattering (SEC–MALS) produced Flory exponent (v) values of 0.475 ± 0.015 for C-NaPSS compared to 0.57 ± 0.02 for NaP4SS, across a range of measured molecular weights. The partial specific volume of NaP4SS was measured to be slightly lower than that of C-NaPSS. Furthermore, C-NaPSS exhibited a glass transition temperature (Tg) of approximately 228 °C with slight variation depending on molecular weight, but no observable Tg was found for NaP4SS over a broad temperature range of −50 to 420 °C. Both polymers showed thermal onsets of degradation in the 420–440 °C range.