The present study deals with the formation of monodisperse sub-micron sized PS/PVP/TiO₂ core- shell hybrid particles via in situ sol-gel method and the effects of varying concentrations of polystyrene seed latex and TBOT, amount and addition rate of water, and sonication power. These reaction factors were found to be closely related to the final particle size, TiO₂ shell thickness, particle density, refractive index, and thermal properties. The particle densities and the refractive indices of the resulting PS/PVP/TiO₂ core-shell hybrid particles were in the range of 2.71~3.69 g/cm³ and 1.63~2.12, respectively.