In this study, polypropylene (PP)/clay nanocomposites containing different concentrations of ethylene-methacrylic acid ionomer (i.e. Surlyn (R)) were prepared, and the effect of ionomer on clay dispersion was studied via WAXD, rheology, SEM, and TEM. The role of the ionomer in the nanocomposites was compared with that of maleic anhydride grafted PP (PP-g-MA), which has been widely used as a compatibilizer in making PP/ clay nanocomposites. With an increase in the concentration of compatibilizer, the position of d(001) peak of OMMT shifted toward a lower angle for PP-g-MA system, while the position remained almost unchanged for Surlyn system, in which a larger interlayer spacing (d(001)) was found with respect to the former. In rheology, the addition of the ionomer led to a gradual increase in both moduli and complex viscosity, and the nonterminal behavior at low frequency was observed in both systems. In addition, the ternary hybrid containing 20 wt % Surlyn achieved the largest enhancement in relative viscosity, which was more than that of the nanocomposite prepared from pure Surlyn or pure PP, presumably indicative of the existence of strong interaction between the components. Finally, SEM and TEM micrographs demonstrated that exfoliated structure was preferred for PP/Surlyn/OMMT hybrids, while intercalated morphology for PP/PP-g-MA/ OMMT. (C) 2007 Wiley Periodicals, Inc.