ABSTRACTPolyacrylate composites with thiol‐modified nanosilica as chain transfer agent were prepared. The FTIR results indicated that the chemical bond has formed between polyacrylate and modified nanosilica. The change of molecular weight distribution proved that the thiol group on the nanosilica surface played the chain transfer agent role just as common thiol. A possible mechanism of modified nanosilica in the polymerization was proposed and the core‐shell may be formed finally. In addition, the dispersion of nanosilica in the polyacrylate also improved as a result of the organic bridge structure between the nanosilica and polyacrylate. The thermal decomposition temperature increased as much as 10°C for polyacrylate with 10 wt % modified nanosilica composites compared to polyacrylate. The coatings hardness increased from 2 to 6 H and the abrasion resistance improved from 28 to 10 mg under the same conditions. Especially, the gloss change of coatings with different content of modified nanosilica indicated that the polyacrylate composites have obviously better aging resistance performance compared to polyacrylate. It may be ascribed to the property that nanosilica can absorb large UV light. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42756.