The dynamic mechanical properties and morphology of novel ethyl acrylate ionomers, poly(ethyl acrylate-co-itaconate) [P(EA-co-ITA)], were investigated. It was found that the P(EA-co-ITA) ionomers showed a well-developed cluster loss tangent peak, which was not seen in poly(styrene-co-itaconate) ionomers. This is probably due to the low matrix T-g of the PEA ionomers, which allows ITA units to form a significant number of multiplets, leading to high clustering. The large difference in the matrix and cluster T-g's was also observed; this is mainly due to two factors. First, the presence of two ion pairs in an ionic repeat unit makes ion-hopping difficult, resulting in higher cluster T-g. Second, the clustering induced by the low matrix T-g naturally increases the cluster T-g. It was also found that the clustering degree was weaker for the itaconate ionomers than for the acrylate ionomers, which is probably due to the fact that the presence of two ion pairs in one ITA unit is more effective in stiffening polymer chains compared to the case of acrylate ionomers. In an SAXS study, an ionomer peak was observed, and the position of the peak shifted to slightly higher angle with increasing ion content, implying that more multiplets form with increasing ion content.