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Séminaire Bernard Binks

Phase Inversion of Nanoparticle-Stabilised Emulsions

Bernard P. Binks

Surfactant & Colloid Group, Department of Chemistry
University of Hull, United Kingdom

We will describe the experimental results concerning the inversion of emulsion type (water-in-oil to oil-in-water and vice versa) of fumed silica particle-stabilised Pickering emulsions with respect to both the inherent particle wettability (quantified by the percentage of residual silanol groups on their surfaces, %SiOH) and the particle concentration. The oils chosen include esters, alcohols and hydrocarbons of varied oil-water interfacial tension. The stability of the emulsions and their preferred drop diameter are influenced by the nearness to phase inversion conditions.
In addition, using a simple model for the surface energy of a particle at the oil-water interface [1], we have calculated the particle contact angle as a function of the particle hydrophobicity for a range of oils (polar to non-polar). Assuming phase inversion occurs around conditions where the contact angle is 90º, good agreement exists between the predicted %SiOH required for phase inversion and the experimental one. A mechanism for inversion induced by particle concentration alone is also advanced.

[1] B.P. Binks and J.H. Clint, Langmuir, 18, 1270 (2002).