The properties and morphology of nanosilica modified with silane coupling agent, methacryloxypropyltrimethoxysilane (MPS), were characterized by fourier transform infrared, zeta potentials, thermogravimetric analysis, and transmission electron microscopy. The results showed that the grafting ratio of MPS on the surface of nanosilica increased with the MPS content. MPS-silica/PBA/PMMA core-shell latexes (MPS-Si/ACR) were prepared by seeded emulsion polymerization. Then they were used to mix with PVC resin. The outer layer (PMMA) enhanced the dispersibility of MPS-Si/ACR in the PVC matrix by increasing the interfacial interaction of these composite particles with PVC. The notched impact strengths of the blends were influenced by the weight ratio of MPS to silica, the concentration of emulsifier (SDS), and the MPS-Si/ACR content. The relationships between the mechanical properties and the core-shell composite structures were elaborated. (c) 2007 Wiley Periodicals, Inc.