Synthesis of micrometer-sized silica-stabilized polystyrene latex particles

Micrometer-sized silica-stabilized polystyrene latexes have been readily prepared by alcoholic dispersion polymerization using a 13 or 2:2 nm commercial alcoholic silica sol as the sole stabilizing agent. These resulting surfactant-free polystyrene particles have relatively narrow particle size distributions and contain surprisingly low levels of silica (<= 1.1% by mass), as judged by disk centrifuge photosedimentometry and thermogravimetry, respectively. Transmission electron microscopy studies indicate that the silica sol is located exclusively at the surface of the polystyrene latex particles at submonolayer coverage. The polymerization of styrene in the absence of the silica sol leads to macroscopic precipitation of the polystyrene. Hence, the presence of silica sol is essential for the colloid stability of these latexes, which presumably involves a charge stabilization mechanism.