Synthesis of polystyrene@silica particles through soap-free emulsion polymerization and sol-gel reaction on polymer surfaces

Polystyrene@silica particles were produced through soap-free emulsion polymerization (SFEP) of styrene and N-vinylacetamide (NVA) via the sol-gel reactions of tetraethyl orthosilicate (TEOS) on polymer particle surfaces. Different amounts of NVA were used to prepare polystyrene particles using the SFEP process. The particles covered with poly-NVA then underwent the Stöber process to form an outer silica shell. NVA was found to stabilize the polymer colloids and improve their stability by steric effects, even after the positive charge on the polymer surface was partially neutralized by the electrostatically adsorbed TEOS, which tends to induce particle aggregation. Further, the –NH functional groups on NVA catalyzed the hydrolysis of TEOS in the sol-gel reaction to form silica. Consequently, small, monodisperse, and stable core-shell particles were formed despite having a low zeta potential.