Eur. Phys. J. Special Topics 222, 39-46 (2013)
https://doi.org/10.1140/epjst/e2013-01824-1

Regular Article

Dynamic surface tension of complex fluid-fluid interfaces: A useful concept, or not?

¹ Food Physics Group, Wageningen University, Bomenweg 2, 6703 HD Wageningen, The Netherlands
² Polymer Physics, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zürich, Switzerland

^a e-mail: leonard.sagis@wur.nl

Received: 16 April 2013
Revised: 23 April 2013
Published online: 17 June 2013

Abstract

Dilatational moduli are typically determined by subjecting interfaces to oscillatory area deformations, and are often defined in terms of the difference between the dynamic or transient surface tension of the interface (the surface tension in its deformed state), and the surface tension of the interface in its non-deformed state. Here we will discuss the usefulness of the dynamic surface tension concept in the characterization of dilatational properties of complex fluid-fluid interfaces. Complex fluid-fluid interfaces are interfaces stabilized by components which form mesophases (two-dimensionional gels, glasses, or (liquid) crystalline phases), as a result of in-plane interactions between the components. We will show that for such interfaces dilatational properties are not exclusively determined by the exchange of surface active components between interface and adjoining bulk phases, but also by in-plane viscoelastic stresses. The separation of these contributions remains a challenging problem which remains to be solved.