We used a novel approach to prepare poly(propylene)-clay nanocomposite starting from pristine montmorillonite and reactive compatibilizer hexadecyl trimethyl ammonium bromide. The nanocomposite structure was revealed by X-ray diffraction and high-resolution electronic microscopy. The thermal properties of the nanocomposite were investigated by thermogravimetric analysis. An increase of thermal stability was observed. (C) 2003 Wiley Periodicals, Inc.