A covalently ftmctionalized organoclay was synthesized successfully through a condensation reaction of SiOH groups on the edge of montmorillonite (MMT) with acryloyl chloride followed by modification with hexadecyltrimethylammonium bromide (CTAB) via an ion-exchange reaction. Fourier transform infrared confirmed that C=C groups had been grafted to MMT sheets. Wide-angle X-ray diffraction measurements showed that CTAB had intercalated into MMT interlayers. The content of bonded acryloyl chloride was 2.42 wt % in the functionalized organoclay according to thermogravimetric analysis. Polypropylene (PP) nanocomposites were prepared by melt mixing. Rheological measurements and morphology observations confirmed that PP nanocomposites containing the organoclay bearing C=C groups exhibited improved interfacial interaction between PP chains and MMT sheets. Thus, the PP nanocomposites showed not only higher storage modulus and complex viscosity values at low frequencies but also enhanced mechanical properties. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1105-1112, 2010