Matthieu Roché (Laboratoire Matière et Systèmes Complexes, Université Paris 7 Denis Diderot)

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22 janvier 11:30 » 12:30 — Bibliothèque PCT - F3.04

Marangoni effect induced by soluble surfactants

The presence of a thermal gradient or surface concentration gradient in surfactant molecules along an interface between two liquids leads to the existence of an interfacial tension gradient and the establishment of a flow in the volume of each liquid. This mechanism is known as the (thermal and/or solutal) Marangoni effect.

During this seminar, I will present the work my collaborators and I have carried out in recent years on the Marangoni solutal effect [1, 2]. Despite its importance in many applications (coating, stability of soap films, etc.), the Marangoni solutal effect has been studied mostly in the case of thin liquid films, and the theoretical interpretation considers the surfactants to be insoluble most of the time. However, the solubility of the surfactants must affect the flow of Marangoni obtained since the molecules can not only move along the interface, but also desorbed to diffuse into the volume.

I will show how we related the properties of the Marangoni flow to the properties of the surfactants (solubility, presence of impurities, geometry of the system, etc.). This link between physicochemistry and hydrodynamics makes it possible to rapidly characterize the solution thermodynamics of surfactants. I will then present a study on the structure of the surface flow [3], to conclude with recent results concerning the flow of Marangoni on salt water.

[1] M.Roché, Z. Li, I. M. Griffiths, S. Le Roux, I. Cantat, A. Saint-Jalmes, and H. A. Stone. Phys. Rev. Lett. 112, 208302 (2014).

[2] S. Le Roux, M. Roché, I. Cantat, and A. Saint-Jalmes, Phys. Rev. E. 93, 13107 (2016).

[3] M. Labousse, B. El Hadj Maïga, I. Cantat, A. Saint-Jalmes, M. Roché, in preparation

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