One-pot synthesis of organo-functionalized monodisperse silica particles in W/O microemulsion and the effect of functional groups on addition into polystyrene

The direct synthesis from TEOS and organosilanes is carried out in W/O microemulsion in order to prepare monodisperse functionalized silica nanoparticles. The well monodisperse particles are obtained successfully from a wide range of concentration of 3-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltrimethoxysilane (MPTMS), phenyltrimethoxysilane (PTMS), vinyltriethoxysilane (VTES) and 3-cyanoethyltriethoxysilane (CETES) in the solution of TEOS and polyoxyethylene nonylphenol ether (NP-5). The particle size can be controlled without widening the distributions. On the other hand, the direct synthesis with these organosilanes and TEOS by conventional Stober method using no surfactant provides colloidal solutions with DLS plots with wide or bimodal dispersions. NP-5 is removed by washing the colloids with DEGDEE and the decline of IR absorptions due to the benzene ring stretching is observed. The resultant colloidal powder is occluded into polystyrene by the polymerization of styrene monomer in the presence of these functionalized silica nanoparticles. The heat resistance of modified polystyrene is investigated by TG-DTA in dry air. The position of DTA peak due to combustion of the polymer is shifted to a higher temperature with the addition of silica nanoparticles. The considerably large shift is found in silica nanoparticles prepared with VIES and PTMS, whose difference is higher than that by the addition of simple silica nanoparticle with no functional groups. (C) 2010 Elsevier B.V. All rights reserved.