Polymer-layered silicate nanocomposites of poly(methyl methacrylate) (PMMA) and an organically modified silicate [tetraallkyl ditallow ammonium bentonite (B34)] system prepared via melt intercalation were studied. The saturation ratio of PMMA to B34 was 25:75 (w/w), as determined by dynamic mechanical thermal analysis, differential scanning calorimetry, and X-ray diffraction. The interaction between PMMA and B34 was detected by Fourier transform infrared spectrometry, which showed two new absorption bands of PMMA/B34 hybrids in comparison with unannealed physical mixtures of PMMA and B34. The degradation temperature of the PMMA/B34 hybrids was 26 degreesC higher than that of neat PMMA according to thermogravimetric analysis, the thermal stability of the hybrids having been enhanced. The glass-transition temperature of excess PMMA remaining outside the clay galleries was about 12-19 degreesC higher than that of neat PMMA. A structural model of the hybrid was also presented. It involves some PMMA chains diffusing into the gallery of B34 and expanding it by 6.8 Angstrom and some penetrating and interacting with the organic chains of the modified cations. Some of the PMMA chains partly contained inside the clay layers were entangled with those remaining outside when PMMA in excess of the saturation ratio was used. (C) 2004 Wiley Periodicals, Inc.