Synergistic stabilization and tunable structures of Pickering high internal phase emulsions by nanoparticles and surfactants

Abstract

The preparation of Pickering emulsions with an internal phase volume fraction of exceeding 95% is still a challenge to date. In this work, Pickering high internal phase emulsions (HIPEs) with an ultrahigh internal phase fraction of 98.5% were prepared using hydrophobic silica nanoparticles (H30) and nonionic surfactant of Span 85 as a dual emulsifier system. Water-in-hexane (W/O) HIPEs stabilized by a mixture of H30 and Span 85 were investigated. Increasing Span 85 concentration in mixture would result in the appearance of smaller droplets of several to tens of micrometers in the HIPEs while a population of large droplets of hundreds of micrometers would appear with increasing H30 concentration. Furthermore, the influences of Span 85 and H30 on the formation of HIPEs were investigated from the polymerized HIPEs (polyHIPEs) synthesized through these HIPEs templates using styrene as the oil phase. The synergism between particles and surfactant exists and plays a crucial role in the stability of HIPEs. This research opens up a new insight into the fabrication of Pickering HIPEs with an ultrahigh internal phase fraction.