Effect of alcohol chain length on particle growth in a mixed solvent system

Abstract

The preparation of microsized uniform silica particles by the hydrolysis and condensation of concentrated tetraethylorthosilicate (TEOS) solutions has been studied in various solvent systems (methanol and ethanol with various long-chain alcohols). Ammonium hydroxide was used not only to initiate hydrolysis and condensation of TEOS, but also to provide the particles with a negative, stabilizing surface charge. Long-chain alcohol was introduced to control the hydrolysis/condensation rate and to reduce the polarity of the system (modified seed growth), as well as to stabilize large particles. To prepare large particles with good uniformity, the solvent composition is important because it determines the stability of both small oligomers and grown particles. The concentration of small seed particles suspended in a solvent and the amount of monomer are also found to be important process parameters in controlling the size and morphology of microspheres. No salt was added to change the surface potential of silica particles. Monodispersed spherical silica particles over 2 pin could be obtained. Moreover, a turbidity experiment showed that the silica growth and nucleation proceeded mainly through the reaction of small oligomers rather than monomeric species.