The interface structure of the polyethylene terephthalate) (PET)/silica nanocomposites was characterized by Fourier transform infrared and solid-state nuclear magnetic resonance. Our study reveals that PET chains are grafted onto the surface of silica nanoparticles, and they form branched and lightly crosslinking structures during the polycondensation. Gel permeation chromatography measurements indicate that the grafted PET chains have a lower molecular weight and broader distribution. Furthermore, a model has been developed to elucidate the interaction of an entanglement network between silica and PET chains that lead to enhancements of G', G '' and eta* values of PET/2 wt% silica nanocotnposites. (c) 2009 Published by Elsevier Ltd.