From individual liquid films to macroscopic foam dynamics: a comparison between polymers and a non-ionic surfactant

Alesya Mikhailovskaya (1) , Emmanouil Chatzigiannakis (2) , Damian Renggli (3) , Jan Vermant (3) , Cécile Monteux (4)

1 ICMPE - Institut de Chimie et des Matériaux Paris-Est
2 TU/e - Eindhoven University of Technology [Eindhoven]
3 D-MATL - Department of Materials [ETH Zürich]
4 SIMM - Sciences et Ingénierie de la Matière Molle (UMR 7615)

Foams can resist destabilizaton in ways which appear similar on a macroscopic scale, but the microscopic origins of the stability and the loss thereof can be quite diverse. Here we compare both the macroscopic drainage and ultimate collapse of aqueous foams stabilized by either a partially hydrolyzed poly(vinyl alcohol) (PVA) or a non-ionic low molecular weight surfactant (BrijO10) with the dynamics of individual thin films at the microscale. From this comparison we gain significant insight regarding the effect of both surface stresses and intermolecular forces on macroscopic foam stability. Distinct regimes in the lifetime of the foams were observed. Drainage at early stages is controlled by the different stress-boundary conditions at the surfaces of the bubbles between the polymer and the surfactant. The stress-carrying capacity of PVA-stabilized interfaces is a result of the mutual contribution of Marangoni stresses and surface shear viscosity. In contrast, surface shear inviscidity and much weaker Marangoni stresses where observed for the non-ionic surfactant surfaces, resulting in faster drainage times, both at the level of the single film and the macroscopic foam. At longer times, the PVA foams present a regime of homogeneous coalescence where isolated coalescence events are observed. This regime which is observed only for PVA foams occurs when the capillary pressure reaches the maximum disjoining pressure. A final regime is then observed for both systems where a fast coalescence front propagates from the top to the bottom of the foams. The critical liquid fractions and capillary pressures at which this regime is obtained are similar for both PVA and BrijO10 foams, which most likely indicates that collapse is related to a universal mechanism which seems unrelated to the stabilizer interfacial dynamics.

Domaines: Chimie

Alesya Mikhailovskaya, Emmanouil Chatzigiannakis, Damian Renggli, Jan Vermant, Cécile Monteux. From individual liquid films to macroscopic foam dynamics: a comparison between polymers and a non-ionic surfactant. Langmuir, 2022, 38 (35), ⟨10.1021/acs.langmuir.2c00900⟩. ⟨hal-03797624⟩