Submicron silica/polystyrene composite particles prepared by a one-step sol-gel process

We describe a convenient, one-step sol-gel route to composite polymeric organic-inorganic particles. The synthesis is based on performing the sol-gel polycondensation within a surfactant-stabilized emulsion of a solution of a polymer - polystyrene of various molecular weights - in tetraethoxysilane, with or without toluene, all dispersed in a basic ethanolic medium. The parameters that dictate the formation of the composite bicontinuous particles were explored and characterized by several methods including TEM, surface area and porosity measurements, high-resolution XPS, TGA, DSC, UV, and FTIR spectroscopies. The particles are obtained in monomodal distributions with diameters in the range of 200-500 nm, depending on the preparation conditions. The polystyrene phase is extractable, and when this extraction is carried out porous silica particles are obtained. Likewise, partial extraction leads to core-shell architecture. The particles were also found to be good carriers for entrapped dye molecules with no leaching. Because of the hybrid nature of the particles, both hydrophobic dyes (Sudan III and IV) and hydrophilic dyes (the cationic Nile blue A) can be entrapped, utilizing the hydrophobic/hydrophilic phases of this composite material, respectively.