Poly(glycidyl methacrylate)/Na-montmorillonite nanocomposites were synthesized by free-radical polymerization of glycidyl methacrylate containing dispersed montmorillonite. By changing the concentration of glycidyl methacrylate several polymer-clay nanocomposites were prepared and the resulting nanocomposites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results indicated that the properties of the composite were significantly improved. The thermogravimetric analysis results revealed that the degradation temperatures of nanocomposites were higher than that of pure polymer and the thermal degradation rates decreased. Examination of these materials by scanning electron microscopy showed that the clay layers are dispersed homogenously in the polymer matrix and the formation of intercalation nanostructure. Furthermore, adsorptive, moisture regain, and water uptake properties of nanocomposites were also investigated. (C) 2004 Wiley Periodicals, Inc.