Miscibility of Polystyrene-Based Ionomers with Poly(2,6-dimethyl-1,4-phenylene oxide)

Sulfonated and carboxylated styrenic ionomers are investigated for their miscibilities with poly(2,6-dimethyl-1,4-phenylene oxide) (PXE), a nonassociating polymer. The nanoscale phase separation in the ionomer component presents a barrier to miscibility, which is nonetheless possible when the functionalization level or PXE content is low. The ionomers absorb PXE up to a certain level, beyond which additional PXE forms a pure phase. As the level of added PXE approaches the saturation limit, ionic groups can be forced from aggregates into the matrix. The saturation limit diminishes as the ionomer's functionalization level increases, but it also depends on the ion type, with ZnSPS showing the highest miscibility of all ionomers studied. The differences in miscibility thus depend on the morphology of the pure ionomer and the strength of the ionic associations.