Surface phase transitions in foams and emulsions

TL;DR

Surface phase transitions in surfactant layers significantly influence foam and emulsion behaviors, offering new control methods, but require deeper understanding for full exploitation.

Contribution

This review highlights emerging opportunities in controlling foam and emulsion properties through surface phase transitions, focusing on surfactant mixtures, natural surfactants, and emulsion phenomena.

Findings

Surface phase transitions affect foam and emulsion properties.

Surfactant mixtures can induce phase transitions on bubble surfaces.

Natural surfactants like saponins form highly viscoelastic layers.

Abstract

Surface phase transitions in surfactant adsorption layers are known to affect the dynamic properties of foams and to induce surface nucleation in freezing emulsion drops. Recently, these transitions were found to play a role in several other phenomena, opening new opportunities for controlling foam and emulsion properties. This review presents a brief outlook of the emerging opportunities in this area. Three topics are emphasized: (1) The use of surfactant mixtures for inducing phase transitions on bubble surfaces in foams; (2) The peculiar properties of natural surfactants saponins which form extremely viscoelastic surface layers; and (3) The main phenomena in emulsions, for which the surface phase transitions are important. The overall conclusion from the reviewed literature is that surface phase transitions could be used as a powerful tool to control many foam and emulsion properties, but we need deeper understanding of the underlying phenomena to explore fully these opportunities.