Dispersion stability and rheological behavior of suspensions of polystyrene coated fumed silica particles in polystyrene solutions

Polystyrene coated silica (SiO2@PS) core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface of γ-methacryloxypropyltrimethoxysilane grafted SiO2 nanoparticles of 20–50 nm in diameter. Rheological behavior and dispersion stability of SiO2@PS suspension in 10 wt% PS solution were compared with suspensions of untreated SiO2 and silane modified SiO2 nanoparticles. Suspensions of the untreated and the silane modified SiO2 exhibited obvious shear thinning. The SiO2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO2 at low shear rates. Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions, implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.