Polyelectrolyte-assisted synthesis of polystyrene microspheres by dispersion polymerization and the subsequent formation of silica shell.

Polystyrene (PS) microspheres were synthesized via dispersion polymerization in alcoholic media. A cationic polyelectrolyte, polyethyleneimine (PEI) was successfully used as a steric stabilizer. The concentration of initiator, monomer, and the solubility parameter of medium showed typical phenomena observed in dispersion polymerization. However, the sensitivity to the change in the particles size was almost twofold greater than conventional stabilizers. Spherical PS particles were synthesized with the PEI concentrations ranging from 5 to 20 wt.% to styrene, but conversion over 95% was achieved over 10 wt.% PEI. As-prepared PEI-stabilized PS microspheres were used as the template for the subsequent formation of a silica shell. As a result, a robust silica layer was fabricated on PS microspheres due to the increased interaction between PEI and tetraethyl orthosilicate (TEOS).