Monodispersed Composite Particles Prepared via Emulsifier-Free Emulsion Polymerization Using Waterborne Polyurethane as Microreactors

Monodispersed Monodispersed polystyrene particles in submicrometer size were intriguingly prepared through emulsifier-free batch-seeded emulsion polymerization using nonmonodispersed waterborne polyurethane (WBPU) beads as microreactors. Different feed ratios of styrene (St)/WBPU for the preparation of composite particles were investigated, and the size-growth course was experimentally followed. The morphology and dispersity of the particles were characterized by scanning electron microscopy together with dynamic laser scattering particle size analyzer. Their inside structure was further characterized by transmission electron microscopy with ultramicrotomy combined with X-ray photoelectron spectroscopy for the composite particles' surface analysis. The probable grafting polymerization of St from WBPU was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance instrument. The obtained composite particles were again employed as the seeds in the emulsion copolymerization of methyl methacrylate. As a result, the formed multilayered composite particles with reverse core-shell structure were also monodispersed and spherical. The mechanism of the formation of the monodispersed particles was proposed. (C) 2014 Wiley Periodicals, Inc.