Preparation of Novel Suspensions of ZnO/Living Block Copolymer Latex Nanoparticles via Pickering Emulsion Polymerization and Their Long Term Stability

In this work, we present the first Pickering emulsion polymerization with a controlled/living character. Pickering emulsion polymerization in the presence of a novel suspension of zinc oxide/poly(sodium 4-styrenesulfonate) (ZnO/PSS-) nano-composite particles was applied to prepare ZnO/living block copolymer latexes. In the emulsion system, 1,1-diphenylethene (DPE)-controlled radical polymerization of poly(methyl methacrylate)-b-poly(butyl acrylate) (PMMA-b-PBA) was proceeded in oil phase. The nanocomposite particles of ZnO/PSS with an average diameter of 20 nm and negatively charged zeta potential around -30 mV were synthesized via hydrothermal method then served as an effective emulsion stabilizer at the oil/water interface. Living polymerization was carried out using DPE-capped PMMA as the macroinitiator and PMMA-b-PBA block copolymer latex was successfully prepared with coverage of ZnO/PSS- nanoparticles. Narrow size distributions of the droplets as well as latex particles were obtained, and the livingness of block copolymers was comparable to that of emulsions stabilized by conventional surfactants. The controlled/living character in Pickering emulsion polymerization was slightly influenced by the amount of PSS- immobilized into the ZnO/PSS- nanoparticles, whereas it was significantly influenced by the weight ratios between ZnO/PSS- and oil phase. The Pickering latexes showed excellent long term stability against either coalescence or sedimentation over several months. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3524-3535, 2011