We have developed a one-step method for preparing nanocomposites based on powdered isotactic polypropylene (i-PP) as a matrix polymer (melt-flow index (MFI) = 7.2 g 10 min(-1)), oligo(i-PP-g-MA) (MFI = 35-70 g 10 min(-1)) as a reactive compatibilizer and docecylamine-surface-modified montmorillonite clay (organo-MMT). This method includes grafting maleic anhydride (MA) onto i-PP chains in the melt state under the controlled thermal degradation conditions and intercalative compounding of the obtained oligo(i-PP-g-MA) with i-PP and organo-MMT by reactive extrusion. The effect of extrusion parameters on MR, composition and properties of the grafted i-PPs, and mechanism of formation and properties of PP/oligo(PP-g-MA)s/organo-MMT nanocomposites were investigated by FTIR, XRD, and thermal analysis (DSC, TGA, and DTA). The results indicate that the formation of nanostructured morphologies proceeds through the formation of strong H-bonding and amidization/imidization reactions between the anhydride units of exfoliated grafted i-PP chain and alkylamine within the organo-MMT interlayers. (c) 2007 Wiley Periodicals, Inc.