PREPARATION OF NARROW SIZE DISTRIBUTION SILICA PARTICLES USING MICROEMULSIONS

Monodisperse silica particles were prepared in microemulsion media usi ng block copolymers and nonionic surfactants. The silica particles wer e obtained by hydrolysis and condensation of tetraethoxysilane, using Mis as a catalyst, and they were characterized by optical and electron microscopy, nitrogen sorption, Fourier transform infrared spectroscop y and thin-layer chromatography. Particles, with average sizes from 0. 1 to 1.5 mu m and with specific surfaces lower than 100 m(2)/g could b e obtained. The results showed that the size could be controlled by bo th the cosurfactant chain length and concentration. The higher the cos urfactant concentration and the shorter the chain length, the larger t he particles. This has been attributed to the increase of interfacial flexibility with reduction of chain length. This causes an increase in the velocity of particle growth, then producing larger particles.