Synthesis of Multipod-like Silica/Polymer Latex Particles
via Nitroxide-Mediated Polymerization-Induced Self-Assembly of Amphiphilic
Block Copolymers
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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[(PEOMA<sub>950</sub>)<sub>12</sub>-<i>co</i>-S<sub>1</sub>]-SG1, <i>M</i><sub>n</sub> = 11 700 g mol<sup>–1</sup> and <i>M</i><sub>w</sub>/<i>M</i><sub>n</sub> = 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 <i>n</i>-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