The Stability of Highly Concentrated Water-in-Oil Emulsions and Structure of Highly Porous Polystyrene Produced from Them

Abstract

The porosity of polymer materials produced by polymerizing dispersion media of highly concentrated emulsions may be predicted, provided that the emulsions are stable. The study of the stability of water-in-oil (W/O) emulsions containing styrene as a dispersion medium at 25 and 65°C has shown that emulsions with a dispersed phase fraction of 0.75 and sorbitan monooleate concentrations of 1.5–20.0 vol % are stable to coalescence but are unstable to sedimentation. Emulsions with a dispersed phase fraction of 0.95 are stable to both coalescence and sedimentation at sorbitan monooleate concentrations of 10–20 vol %. Open-pore polymer materials are formed from emulsions with dispersed phase fractions of 0.75 and 0.95 at sorbitan monooleate concentrations of 2.0–3.5 and 10–12 vol %, respectively. At a dispersed phase fraction of 0.75 and a sorbitan monooleate concentration of <2 vol %, a multiple O/W/O emulsion is formed, the polymerization of which yields a porous polymer material containing spherical polystyrene particles inside pores. At higher surfactant concentrations in emulsions with dispersed phase fractions of 0.75 and 0.95 partly destroyed porous materials are formed.