It has been known for more than a century that colloidal particles with the “right” wetting
properties can stabilize emulsions, much like surfactants or amphiphilic polymers do. Today, particlestabilized
emulsions (so-called Pickering emulsions) play an important role in many industrial applications,
but our fundamental understanding of the connection between particle properties and emulsion characteristics
is still surprisingly poor. We can, for example, prepare an emulsion by mixing equal amounts of an oil phase
and an aqueous particle dispersion; but even with complete knowledge of both liquids and all particle
properties, current theory fails to predict reliably the stability and even the type (w/o or o/w) of the emulsion
formed. This presentation will discuss the source of such difficulties and propose several steps toward an improved
theoretical description and better practical control of emulsion properties. In particular, I will address the role
of electrostatic interactions between a particle and a liquid interface before and after particle adsorption, and
show that widely neglected “image forces” can prevent particle adsorption and emulsion stabilization
altogether. For the case of successful particle adsorption, the particle’s contact angle with the interface is
found to be influenced strongly by the particle charge and surface roughness in ways that are not usually accounted for, but have important consequences for the long term stability of Pickering emulsions.
https://mediaspace.gatech.edu/media/behrens/1_tl9xqvfx
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