A set of organically modified clays (OLS) were mixed with different compatibilizers to alter their interactions with either homopolymer or heterophasic polypropylenes when they were melt-mixed, and the relation between the OLS/compatibilizer system and the composite morphology was studied. X-ray diffraction (XRD) showed that depending on the specific OLS/compatibilizer system, it is possible to obtain several morphologies in the composites. In particular, some samples prepared with compatibilizers based on itaconic acid and OLSs, which had the highest cation exchange capacity and were organically modified with a set of quaternary ammonium salts, presented longer clay interlayer distances than the original OLSs, whereas other composites showed a clay collapse associated with shorter interlayer distances. Moreover, some composites presented both kinds of morphologies together. By means of diffuse reflectance spectroscopy and thermogravimetric analysis, it was possible to show that the OLSs were stable under the operating conditions, so the decrease in the interlayer distance found in some samples was not related to degradation processes. On the other hand, high-resolution transmission electron microscopy (HR-TEM) showed that collapsed clays were formed by tactoid and immiscible structures with poor dispersion in the polymer matrix. However, samples with intercalate state from XRD presented very well dispersed multilayer stacks about 10 nm thick. Finally, those samples with both collapsed and intercalate morphologies presented tactoid and immiscible structures together with well dispersed multilayer stacks in the corresponding HR-TEM images. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 1278-1286, 2009