Reactive mineral powders were prepared with a vinyl monomer as an intercalating agent, which was grafted onto the surface of nanoclay layers, to offer crosslinking points between the nanoclay layers. According to IR characterization, the vinyl group of (3-acrylamidopropyl)trimethylammonium chloride, grafted onto the clay, disappeared after polymerization was performed. This spectral evidence confirmed that the reaction occurred between the clay layers. Thermogravimetric curves showed that the weight percentage remaining at 750 degrees C for the intercalated clay/sodium acrylate nanocomposites was about 5 wt % higher than that for organic poly(sodium acrylate). This indicated that the clay was not diminished in the polymerization, and this process produced intercalated mica with a quaternary ammonium content of approximately 38.8 mmol/100 g and intercalated montmorillonite with a quaternary, ammonium content of approximately 45.36 mmol/ 100 g. We also investigated the effect of reactive clays on the crystalline morphology and water absorbency for these nanocomposite hydrogels. (c) 2005 Wiley Periodicals, Inc.