Abstract: The rheological properties of 0.98%(molar frac‘tion) lightly sulfonated polystyrene ionomer(SPS), zinc neutralized SPS(ZnSPS) and their blends with precursor polystyrene(PS) are reported. It is found that the rheological properties of ionomers and their blends are quite different with PS, due to the ionic aggregates acting as physical cross links in ionomers. Using linear viscoelasticity data, the time-temperature superposition can be conducted to all samples. Differences are also found in the low frequency region of linear viscoelasticity data. Correlated with the relaxation of polymer chains, the moduli of ionomers are higher than those of PSdue to the effect of ionic aggregates. In the steady shear test, typical yield phenomena can be found in the apparent viscosity curves of ionomers, which are also resulted from the ionic aggregates. Utracki's formula for yield stress fits the apparent viscosity data properly and the yield stress and zero shear viscosity of ionomers are obtained. It is also found that the yield phenomena of ionomers are disappeared above certain temperature. The Cox-Merz rule is invalid for ionomers, due to the complex viscosity and apparent viscosity characterizes at different state of ionomer fluid, with ionic aggregates and breakdown of ionic aggregates, respectively. Finally, the different relationship between blends composition and rheological properties indicate that different ionic aggregate structure or ionic association exists in the PS/SPSand PS/ZnSPSblends.

Key words: Rheological properties, Sulfonated polystyrene ionomers, Yield stress, Blends