To have a better insight into the effect of interaction between polymer matrix and clay on the properties of nanocomposite, poly(methyl methacrylate)/clay nanocomposites were prepared by a heterocoagulation method. Using a reactive cationic emulsifier, methacryloyloxyethyltrimethyl ammonium chloride (METAC), a strong polymer-clay interaction was obtained with the advantage of keeping a consistent polymer matrix property. X-ray diffraction and transmission electronic microscopy indicated an exfoliated structure in nanocomposites. The glass transition temperature (T-g) of the nanocomposites was measured by DSC and DMA. The DMA results showed that with a strong interaction, PMMA-METAC nanocomposite showed a 20 degrees C enhancement in glass transition temperature (Tg), whereas a slight increase in Tg was observed for PMMA-cetyl trimethylammonium bromide (CTAB)/clay nanocomposite with a weak interaction. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 733-738, 2010