Capillary force induced formation of monodisperse polystyrene/silica organic-inorganic hybrid hollow spheres.

This paper presents a "one-spot" procedure to fabricate polystyrene/silica (PS/SiO(2)) hybrid hollow spheres. In this approach, when poly(vinylpyrrolidone)-stabilized PS colloids were deposited by sol-gel derived silica layer under acidic medium, it was interesting to find that the PS/SiO(2) core-shell colloids gradually changed to hollow structure spontaneously in the same medium as reaction went on. The formation of this hollow structure should be attributed to the diffusion of PS macromolecular chains from core particles into the voids between silica nanoparticles driven by the strong capillary force.