A novel preparation method of raspberry-like PMMA/SiO2 hybrid microspheres

This paper presents a novel method for preparation of raspberry-like organic-inorganic hybrid microspheres with PMMA as core and nanosilica particles as shell. A cationic monomer, 2-(methacryloyl)ethyltrimethylammonium chloride (MTC), was used as an auxiliary monomer, and nanosilica particles were deposited onto the surfaces of organic particles in aqueous medium via electrostatic interaction between nanosilica particles and MTC. The whole process required neither surface treatment for nanosilica particles nor additional surfactant or stabilizer. TEM indicated that electrostatic interaction between negatively charged silica and positively charged MTC was strong enough for the formation of colloidally stable hybrid microspheres with raspberry-like morphology. The average particle sizes and the final silica contents of the hybrid microspheres ranged from 180 to 600 nm and 15 to 60 wt %, respectively. A possible formation mechanism of the raspberry-like hybrid microspheres was proposed on the basis of the effects of some influencing parameters, for instance, diameters and amount of the silica particles, MTC and APS concentration on the polymerization stability, diameters, silica content, and morphology of the hybrid microspheres.