Penetration of surfactant solutions into hydrophobic capillaries

Abstract

The initial rise velocity of surfactant solutions in hydrophobic capillaries is independent of time (F. Tiberg, B. Zhmud, K. Hallstensson and M. von Bahr, Phys. Chem. Chem. Phys., 2000, 2, 5189). By analogy with the hydrodynamics of an overflowing cylinder, we present a steady-state solution for capillary penetration in which the velocity is determined by the adsorption kinetics at the air–water interface. Good agreement between the model predictions and experimental data of Tiberg and coworkers is obtained for the non-ionic surfactant C₁₀E₆ under the assumption of diffusion-controlled adsorption. The longer chain homologue, C₁₄E₆, shows evidence of kinetic barriers to adsorption.