Silica nanoparticles as surfactants and fillers for latexes made by miniemulsion polymerization

Polymer dispersions made of a variety of monomers, including styrene, butyl acrylate, and methyl methacrylate, were generated by the miniemulsion process in the presence of a coupling comonomer, a hydrophobe, and silica nanoparticles. Depending on the reaction conditions and the surfactants employed, different hybrid morphologies were obtained, comprising a "hedgehog" structure where the silica surrounds the latex droplet and provides stabilization even without any low molecular weight surfactant. In other parts of the composition diagram noncoupled structures as well as "raspberry" hybrids where whole clusters of silica nanoparticles are completely embedded in the polymer particle can be made. The resulting structures are promising for a number of applications, e.g. the increase of scratch resistance in water-based coatings.