Synthesis of Multipod-like Silica/Polymer Latex Particles via Nitroxide-Mediated Polymerization-Induced Self-Assembly of Amphiphilic Block Copolymers

Abstract

We report the first nitroxide-mediated synthesis of multipod-like silica/polymer latexes by polymerization-induced self-assembly (PISA) of amphiphilic block copolymers in aqueous emulsion. A water-soluble brush-type PEO-based macroalkoxyamine initiator composed of poly(ethylene oxide) methacrylate and a small amount of styrene (P[(PEOMA950)12-co-S1]-SG1, Mn = 11 700 g mol–1 and Mw/Mn = 1.11) was synthesized and physically adsorbed on the surface of silica particles through hydrogen-bonding interactions. The adsorbed macroalkoxyamine initiator was subsequently employed to initiate the emulsion polymerization of n-butyl methacrylate with a small amount of styrene under mild conditions (85 °C). Kinetic analysis indicates that the polymerizations exhibit the same behavior (i.e., the same reaction rates and the same level of control) as those reported in our previous work in the absence of silica under otherwise similar experimental conditions [Qiao Macromolecules 2013, 46, 4285−4295]. This observation is fully consistent with a PISA process taking place at the silica surface. The resulting self-assembled block copolymers formed polymer nodules randomly distributed around the central silica spheres. Varying the macroinitiator concentration or the silica particle size enabled the successful formation of hybrid particles with dumbbell-, daisy-, or raspberry-like morphologies using this new surface-PISA process.