We prepared novel poly(methyl methacrylate) (PMMA)/CaCO3 nanocomposites by using reverse micelle as a template. The nanoparticles of CaCO3 were prepared by the reverse microemulsion with functional monomer, methyl methacrylate (MMA) as oily phase, and the PMMA/CaCO3 nanocomposite was obtained via polymerization of MMA monomer. The SEM image showed that the nanoparticles of CaCO3 were dispersed in the polymer matrix. Dynamic mechanical analysis (DMTA) was performed to investigate the interaction between the nanoparticles and the polymer chains. In the low-temperature ripening process, two tan delta peaks were observed in the nanocomposite, corresponding to the glass transitions of the matrix and the interface layer. In the high-temperature ripening process, only one tan delta peak was observed, suggesting that the interface layer forms a continuous phase. The nanoparticles behave as a physical crosslinker in the interface layer. Modification of the surface of nanoparticles with polyacrylamide and poly(N,N'-methylenedisacrylamide) in the nanocomposite did not show an appreciable effect on the interaction of nanoparticles with the matrix. Upon removal of the aqueous phase around the nanoparticles, we obtained surface-capped nanoparticles by using an improved reverse microemulsion technique. Another PMMA/CaCO3 nanocomposite was also obtained with these modified nanoparticles. DMTA analysis of this nanocomposite demonstrated that the aqueous phase layer around the nanoparticles does not significantly affect the interaction between the nanoparticles and the polymer chains. (C) 2004 Wiley Periodicals, Inc.