Unlike spherical polymer particles, non-spherical particles have attracted a great deal of attention in a variety of applications due to their specific properties. Therefore, many types of methods for designing the morphology of polymer particles have been developed. Among these methods, seeded emulsion polymerization (SEP) is drawing attention as one of effective approaches for designing particle morphology. In general, since the particle morphology is determined by the relationship between thermodynamic and kinetics, solid particles such as polystyrene (PS) are used as seeds due to compatibility with hydrophobic monomer. Under such circumstances, we have discovered that a series of raspberry-shaped composite microgels can be synthesized by SEP of styrene using “microgel” containing hydrophilic or amphiphilic polymer chains as a seed (Figure (a)).<sup>1 </sup>Microgels are water swelling and hydrophobic substances different from solid particles. Therefore, the relationship between the properties of the local micro-hydrogel environment such as polarity and hydrophobicity, and the function as the nucleation site of the hydrophobic PS was unknown. In this study, we focused on the polarity within the microgels and investigated the effect of the charge distribution in the core microgels on the structure of the resulting composite microgels. In the case of charged microgels in which the carboxyl-groups are located on the center of microgels, the solid nanoparticles formed only the surface of the seed microgels (Figure (b)). Conversely, the microgel cores were occupied by hydrophobic solid particles in the case of charged microgels with carboxyl groups located on surface of microgels (Figure (c)). From these results, it was concluded that styrene monomer may penetrate into the polyelectrolyte hydrogel layer. However, the resultant polystyrene nanoparticles obtained do not like combinations with polyelectrolyte hydrogels.<sup>2 </sup>

Nanocomposite microgels formed by seeded emulsion polymerization in the presence of radially structured polyelectrolyte microgels

255th National Meeting (2018)

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