BLENDS OF BIPHASIC IONOMERS WITH CHEMICALLY IDENTICAL MONOFUNCTIONAL AND BIFUNCTIONAL OLIGOMERS

Biphasic Cs and Ba carboxylated polystyrene ionomers were blended with chemically identical mono- and bifunctional oligomers whose chain len gths are significantly greater than the average segmental length betwe en ionic groups in the ionomer. The ionomers were chosen to have two i on contents such that, in one case, the matrix phase is dominant and, in the other, the cluster phase is dominant. From dynamic mechanical t hermal analysis, it was observed that the biphasic morphology of the i onomers is preserved in all blends (containing up to 60 wt % oligomer) . The monofunctional oligomers tend to have a mild plasticizing action on the two phases. In the matrix-dominated ionomer, the bifunctional oligomer has an antiplasticization effect at lower oligomer contents; this is attributed to a greater dispersion of ionic aggregates in the matrix phase, accompanied by pinning of the oligomer extremities in mu ltiplets, which prevents plasticizing action. In the cluster-dominated ionomer, the oligomer forms a separate phase, which is related to ins ufficiently large ion-poor styrene regions in the ionomer to accommoda te the long nonionic portion of the oligomer chains.