Foams and DLVO theory

The DLVO theory can be used to analyse foam stabilization by electrostatic repulsion. When a substance is added to a foam leading to the charge of the surface film this can result in the repulsion of the air bubbles coming near to one another. Soap (surfactant) films arc modelled by two air slabs (infinite thickness) with a liquid film in between. The attractive potential is then given by  

The electrostatic potential is expressed by (assuming the Debye-Hiickel approximation is valid)  

Foams are elastic systems because bubbles can be compressed and it may be important to include this effect in a full theoretical DLVO description of foams. 

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