The grafting of poly(acrylic acid) to polypropylene was realized with supercritical CO2 as a Substrate swelling agent and a monomer/initiator carrier. The effects of different supercritical CO2-assisted impregnation conditions on the substrate mass increment and grafting efficiency were studied. The original isotactic polypropylene and the grafting product were characterized through IR spectroscopy, differential scanning calorimetry, and scanning electron microscopy. (c) 2006 Wiley Periodicals, Inc.