Poly(acrylic acid-co-sodium acrylate)/zinc oxide, P(AA-SA)/ZnO, composite latex particles were synthesized by inverse miniemulsion polymerization. The ZnO nanoparticles were prepared by hydrothermal synthesis and undergone oleic acid (OA) surface treatment. The X-ray diffraction pattern and FT-IR spectra characterized the crystal structure and functional groups of OA-ZnO nanoparticles. An appropriate formulation in preparing P(AA-SA) latex particles, ensuring the dominant in situ particle nucleation and growth, was developed in our experiment first. Sodium hydroxide was chosen as a costabilizer, because of its ability to increase the deprotonation of acylic acid and enhance the hydrophilicity of monomer, acrylic acid besides providing osmotic pressure. The growth mechanism of P(AA-SA)/ZnO composite particles was proposed. The CA-ZnO nanoparticles were adsorbed on or around the surface of P(AA-SA) latex particles by hydrophobic interaction, thus enhanced the interfacial tension over latex particles. The P(AA-SA)/ZnO composite latex particles owned better thermal stability than pure latex particles. The pH regulation capacity was excellent for both ZnO and P(AA-SA) particles. Combining P(AA-SA) and ZnO nanoparticles into composite particles, the performance in pH regulation and UV shielding was discussed from our experimental results. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8081-8090, 2008