Synthesis of hybrid hollow sub-microspheres assisted by pre-added colloidal SiO2

A novel method was developed to synthesize organic-inorganic hybrid hollow sub-microspheres (HHSs) through the addition of colloidal SiO2. The hydrolysis rate of 3-(methacryloyloxy)propyltrimethoxysilane (MPS) was accelerated by SiO2 particles; meanwhile, the condensation rate of the hydrolytic species was decelerated. Thus, the hydrolytic monomers and oligomers of MPS were preserved as emulsifiers. These emulsifiers can then emulsify the isopentyl acetate (PEA) to form a steady O/W emulsion. The HHSs were produced by subsequent free radical polymerization and removal of the oil core. The hydrolytic MPS acted as emulsifiers and polymerizable monomers at the emulsification and polymerization stage, respectively. Thus, extra emulsifiers, co-emulsifiers, and organic monomers were omitted, which simplified the synthesis process. The good dispersion of HHSs in water and oil, as well as the EDX results, indicated the organic-inorganic hybrid structure of HHSs.