Foams are interesting materials as their properties (e.g. mechanical or acoustic) are combined with very light weight. However, they are often unstable in time. Foams and emulsions like many two-phase materials suffer from coarsening due to the energy cost, which is associated with the interface that separates both phases. While our understanding of the driving forces and the dynamics of coarsening in different materials is well advanced by now, current research efforts address the question of how this process may be slowed down, or, ideally, arrested.<br/>Many systems including particles have proved very efficient to stabilize foams and/or emulsions against coarsening. Moreover, many studies have questioned the Gibbs criterion, which predicts that coarsening stops if the surface elasticity is larger than half the surface tension.<br/>In this work, we use a model system of two bubbles to explore how the presence of a surface elasticity may interfere with the coarsening process and the final bubble size distribution. Combining experiments and modelling in the analysis of the evolution of two bubbles, we show that clear relationships can be predicted between the surface tension, the surface elasticity and the change in bubble polydispersity. We rationalise these relationships by the introduction of a modified Gibbs criterion. Besides their general interest, the present results have direct implications for our understanding of foam stability.

Arresting bubble coarsening with surface elasticity

254th National Meeting (2017)

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