Surface modification of silica particles was achieved by two-step (acid-base) process in an aqueous solution with organoalkoxysilanes, such as methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), vinyltrimethoxysilane (VTMS), and vinyltriethoxysilane (VTES). The relative hydrolysis and condensation rates of organoalkoxysilanes could be elucidated from the kinetic data that were obtained by measuring the mixing time (hydrolysis) and the turbid time (condensation) in this system. Surface-modified silica particles were prepared by two-step process separating the hydrolysis and condensation procedures to easily control the condensation rate. The size of the surface-modified silica particles could be controlled by the ratio of monomer/silica seed. Control of the condensation rate and colloidal interaction could prevent the self-aggregation between primary particles. The size and morphology of the resulting particles were examined by FE-SEM and TEM. The particles were characterized by FTIR and TGA.

Keywords: silica, two-step process, surface modification, organoalkoxysilanes