Outstanding stability of poorly-protected pickering emulsions

Abstract

Pickering emulsions are surfactant-free emulsions, stabilized solely by colloidal particles. Most of these emulsions exhibit exceptionally high stability and bulk elasticity. In order to investigate the effect of interfacial particle interactions and structure on the emulsions properties, we synthesized particles (silica, core-shell latexes, neighborite cubes) whose interactions can be tuned by a composition variable (pH, ionic strength...) leading to stimulus-responsive materials. The systems could switch from kinetically stable to unstable on demand. Surprisingly, some kinetically stable emulsions were obtained at very low interfacial particle coverage. We demonstrate the generality of this phenomenology using different types of particles and we discuss the origin of the stabilization in the poorly-covered regime. © Springer-Verlag Berlin Heidelberg 2010.