Colloidal particles with complex microstructures via phase separation in swelled polymer microspheres.

Polymer microparticles with complex microstructures, including cut spheres, bowl-like particles, hollow spheres with holes and porous hollow spheres, were prepared via phase separation in polymer microspheres. The incorporation of sulfonic acid groups is crucial, and the resulting microparticles are in sharp contrast to those prepared from regular polystyrene microspheres.