Pickering emulsions stabilized by stacked catanionic micro-crystals controlled by charge regulation

Abstract

In this paper the mechanism behind the stabilization of Pickering emulsions by stacked catanionic micro-crystals is described. A temperature-quench of mixtures of oppositely charged surfactants (catanionics) and tetradecane from above the chain melting temperature to room temperature produces stable oil-in-water (o/w) Pickering emulsions in the absence of Ostwald ripening. The oil droplets are decorated by stacks of crystalline discs. The stacking of these discs is controlled by charge regulation as derived from conductivity, scattering and zeta potential measurements. Catanionic nanodiscs are ideal solid particles to stabilize Pickering emulsions since they present no density difference and a structural surface charge which is controlled by the molar ratio between anionic and cationic components. The contact angle of catanionic nanodiscs at a water/oil interface is also controlled by the nonstoichiometry of the components. The resulting energy of adhesion and the repulsion between droplets is much larger than kT. As a consequence of these unique properties of nanodiscs, this type of emulsions presents an extremely high resistance towards coalescence and creaming, even in the presence of salt.

From faceted vesicles to liquid icoshedra: Where topology and crystallography meet

“…At T = T SE our macro-emulsion is thermodynamically stable, unlike common kinetically-stabilized macroemulsions. We note that similar phenomena, interpreted in terms of Pickering emulsions, have 345 been previously detected for alkane droplets, stabilized by catanionic surfactant mixtures [34].…”

Responsive self-assemblies based on fatty acids

“…Contrary to foaming properties, only one fatty acid aggregated system has been shown to adsorb at oil/water interface leading to the long term stabilization of emulsion at room temperature [62,63]. The Zemb's research group has produced the first Pickering emulsion stabilized by catanionic discs of myristic acid and CTAOH.…”

Aqueous foams stabilized by chitin nanocrystals

“…[3][4][5][6][7] The ability of particles to stabilize interfaces, either oil-water or air-water, has been known already for more than a century, and particle-stabilized interfaces were first reported by Ramsden in 1903. These aerated systems, especially aqueous foams, are usually stabilized by low molecular weight (LMW) surfactants or proteins, but they often suffer from low stability due to many destabilization mechanisms that take place.…”

“…In the last years some considerable amount of work has been performed on investigating the potential of particles as foam stabilizers. [3][4][5][6][7] The ability of particles to stabilize interfaces, either oil-water or air-water, has been known already for more than a century, and particle-stabilized interfaces were first reported by Ramsden in 1903. 8 The work was then continued by Pickering in 1908, 9 after whom this stabilization mechanism was named.…”