Slightly surface-functionalized polystyrene (PS) microspheres are prepared by photocatalytic Pickering emulsion polymerization using sodium styrene sulfonate (SSS)-modified titania hydrosol as a stabilizer. Aqueous electrophoresis measurements indicate the adsorption of bifunctional SSS anions on the surface of titania nanoparticles via electrostatic interaction. SSS molecules participate in the copolymerization with the monomers before the nucleation and thus have a great effect on the morphology and surface structure of the obtained PS microspheres. Appropriate SSS concentration leads to PS microspheres with small size, narrow distribution, and uniform surface chemistry. This kind of polymer particles can be used as a good candidate for the electrophoretic displays because of their high colloidal stability and electrophoretic mobility in the apolar solvent. (C) 2011 Elsevier Inc. All rights reserved.