Interfacial behavior of catanionic surfactants.
We report a dramatic increase in foam stability for catanionic mixtures (myristic acid and cetyl trimethylammonium bromide, CTABr) with respect to that of CTABr solutions. This increase was related to the low surface tension, high surface concentration, and high viscoelastic compression moduli, as measured with rising bubble experiments and ellipsometry. Dialysis of the catanionic mixtures has been used to decrease the concentration of free surfactant ions (CTA(+)). The equilibrium surface tension is reached faster for nondialyzed samples because of the presence of these free ions. As a consequence, the foamability of the dialyzed solutions is lower. Foam coarsening has been studied using multiple light scattering: it is similar for dialyzed and nondialyzed samples and much slower than for pure CTABr foams.
Laboratoire de Physique des Solides, Université Paris-Sud, UMR CNRS 8502, 91405 Orsay Cedex, France.
Antonio
A
Stocco
David
D
Carriere
Maximilien
M
Cottat
Dominique
D
Langevin