Widely dispersed low density polyethylene (LDPE) based nanocomposites (Nc's) were obtained in the melt state thanks to their compatibilization with a zinc ionomer of poly(ethylene-co-methacrylic acid) (Pema-Zn). The variables probed were the ionomer and organoclay content ranging from 0 to 20%, and from 0 to 10%, respectively. The TEM images showed that the organoclay is widely exfoliated. Furthermore, we report for the first time that the organoclay is concentrated in irregular zones. Taking into account the compatibility between MMT and the ionomer, it is plausible that the ionomer clusters are also concentrated in the organoclay-rich regions. This heterogeneous microstructure has a positive effect on the mechanical properties since the Nc's are ductile, and the modulus increases were among the largest reported for LDPE, attaining a 160% increase with a 10% montmorillonite (MMT) content. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 1762-1770, 2011