Vertical concentration gradients of soluble surfactants in the rupture of thin liquid films

Results show that when surfactant diffusion is slow relative to advection and adsorption, substantial surfactant vertical concentration gradients can emerge. These gradients slow down adsorption and increase stabilizing Marangoni stresses, leading the VA approximation to underestimate the rupture time. Significant deviations in predicted rupture time are also observed when the initial bulk and surfactant concentrations are not in equilibrium, which is common in industrial applications.