AbstractBlends of zinc neutralized sulfonated ethylene‐propylene‐diene elastomer (ZnS‐EPDM) with poly(styrene‐co‐vinyl pyridine) have been compared with mixtures of the unfunctionalized rubber with the same copolymer. These binary component blends contain relatively low levels of interacting groups, which are, however, sufficient for the formation of intermolecular complexes. As a result of these interactions, marked enhancement in properties have been observed. In this study, small angle neutron scattering (SANS) is used to determine domain dimensions. The SANS experiments clearly show a decrease in domain size by three orders of magnitude when compatibilization via the sulfonate groups takes place. This reduction correlates with large changes in mechanical p