A core-shell hybrid nanocomposites, possessing a hard core of nano titanium dioxide (n-TiO2) and a soft shell of brushlike polystyrene (PS), were successfully prepared by surface-initiated atom transfer radical polymerization (ATRP) at 90 degrees C in anisole solution using CuBr/PMDETA as the catalyst, in the presence of sacrificial initiator. FTIR, H-1 NMR, XPS, TEM, SEM, TGA, and DSC were used to determine the chemical structure, morphology, thermal properties, and the grafted PS quantities of the resulting products. TEM images of the samples provided direct evidence for the formation of a core-shell structure. The thermal stabilities of the grafted polymers were dramatically elevated relative to that of pristine PS according to TGA results. DSC results demonstrated that the TiO2-PS nanocomposites exhibited higher glass transition temperature (T-g) compared with pristine PS. The molecular weights of the free polymers formed by sacrificial initiator, which were similar to that of surface-attached polymers were measured by GPC instrument which showed that the molecular weights of PS were well controlled with a relatively narrow polydispersity index (PDI < 1.2). (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1782-1790, 2010