Silica encapsulation of liquid PDMS droplets

Core-shell particles have been prepared by the precipitation of a silica layer around cross-linked polydimethylsiloxane (PDMS) microgel core particles. The PDMS microgel particles were first encapsulated in a thin layer of silica by precipitation from a supersaturated sodium silicate solution over the pH range 9-10.5. Subsequently, controlled growth of this shell was achieved by the drop-wise addition of tetraethoxysilane, at lower ethanol concentrations (30 vol.% in water) and higher ammonia concentrations (7.6 M) than are normally used in "Stober-type" silica particle synthesis. Scanning electron microscopy showed that the PDMS microgel particles were typically about 550 nm in diameter, with silica shells of thickness about 120 nm. (C) 1998 Elsevier Science B.V. All rights reserved.