Influence of the polymer backbone rigidity on polyelectrolyte–surfactant complexes at the air/water interface

We report dynamic surface tension and X-ray reflectivity studies on mixed polyelectrolyte–surfactant solutions. We have studied two different polyelectrolytes, polyacrylamide sulfonate, with a flexible backbone and xanthan, with a rigid backbone. We compare the results with the surface rheology and foaming behaviour of the same solutions. The static and dynamic properties of the mixed surface layers are similar for the solutions with the two polymers, only the behaviour upon large compressions is different. This might be at the origin of the differences in foamability and foam film stability observed with the two systems.