The mechanical properties and morphology of homoblends of poly(ethyl acrylate-co-acrylate) (PEAA) having one ion pair per ionic monomer repeat unit and poly(ethyl acrylate-co-itaconate) (PEAITA) having two ion pairs were investigated. It was found that the compositional variation in the ionomer homoblends did not affect the matrix or cluster glass transition temperatures of the two ionomers of the homoblends. It was also observed that the ionomer homoblends showed two ionic plateaus and that the changes in the two ionic moduli were directly related to the relative amounts of the two ionomers. The ionic moduli calculated with the model for filler-dispersed materials were found to fit the experimental data to a great extent. Therefore, it was suggested that the PEAITA/PEAA ionomer homoblends were filler-containing composite materials rather than miscible blends. In the X-ray scattering study, it was observed that the morphology of the ionomer homoblends was not affected by mixing. The results obtained in this work might be useful for the modification of the storage moduli of copolymers in a certain temperature range without the alteration of their processing temperatures. (c) 2007 Wiley Periodicals, Inc.