Surface rheology and foam stability of mixed surfactant-polyelectrolyte solutions

We have studied the surface rheology of mixed solutions of anionic polyelectrolytes and cationic surfactants. Surface elasticity and viscosity exhibit a maximum at a surfactant concentration much smaller than that for solutions of the pure surfactant. Foaming and foam stability were found to depend on these coefficients, although a systematic relation is difficult to establish. Still more surprisingly, the behavior of foams and foam films is very different in these systems.