Polypropylene-clay nanocomposites were prepared by a solution technique and a subsequent melt-mixing process. A titanate coupling agent was used to improve the compatibility of the nanoclay particles with the polypropylene. The dispersion of the nanoclay particles in polypropylene was studied with X-ray diffraction (XRD) and transmission electron microscopy (TEM). An increased d-spacing value of the clay particles in the nanocomposites was observed, and it was compared with the values of as-mined (pristine) and as-received (organophilic) clay particles. The number of intercalated layers in a single clay crystallite was determined to be 4, and the number was confirmed with XRD data and TEM images. On the basis of the Daumas-Herold model (which is widely used for graphite intercalation compounds), the stage 2 and stage 3 structures of montmorillonite particles in polypropylene were recommended. A study on the stage structure suggested a way of determining the presence of polymer molecules in the clay galleries. The results confirmed the existence of single-layered platelets with improved dispersion in polypropylene. © 2005 Wiley Periodicals, Inc.