VISCOELASTIC AND MORPHOLOGICAL-STUDY OF IONIC AGGREGATES IN IONOMERS AND IONOMER BLENDS

Aggregation of the ionic groups in blends of sulfonated polystyrene (S PS) with ethyl acrylate/4-vinylpyridine and styrene/4-vinylpyridine co polymers was investigated by dynamic mechanical thermal analysis (DMTA ) and small-angle X-ray scattering (SAXS). Viscoelastic measurements s how the existence of a high-temperature loss peak, similar to the peak observed in ionomers. However, the temperature of the transition is d epressed relative to the parent ionomers due to internal plasticizatio n. The presence of ionic aggregates was confirmed by calculating the a verage network functionalities and by the failure of frequency-tempera ture superposition. Activation energies for the high-temperature trans ition are related to the relative strengths of the interactions, which is consistent with the transition being due to motion of the ionic gr oups. SAXS measurements show that the ''ionic peak'' present in ionome rs is destroyed upon blending. The data are discussed in terms of mode ls for ionomer morphology.