About the suitability of the seeded-dispersion polymerization technique for preparing micron-sized silica-polystyrene clusters

Dispersion polymerization of styrene was performed in the presence of methacryloxymethyltrimethoxysilane-derivatized silica seeds in various experimental conditions in order to get micron-sized polystyrene/silica clusters of controlled morphology. It is demonstrated that asymmetric clusters (dumbbell-like or snowman-like) are easily prepared in a large range of sizes by taking advantage of the coalescence phenomenon which occurs between growing polymer nodules in pure alcoholic medium, at high monomer concentration and/or at high temperature. A model describing the evolution of the morphologies as a function of the seed size and concentration is proposed. Moreover, micron-sized multipod-like or raspberry-like particles were also obtained by adding water in the dispersing medium. The experimental parameters which allow control of the cluster morphology are compared to those of the seeded-emulsion polymerization, which is efficient for preparing submicron-sized clusters.