Surfactant self-assembly near contact lines: Control of advancing surfactant solutions

When a substrate is immersed into a solution of strongly adsorbing surfactant, the contact line advances by jumping forward along the surface. If a drop of the solution is placed on the surface, it autophobes. We have directly observed the surfactant structure ahead of the contact line which causes this behavior. This adsorbed, self-assembled structure exhibits two regions with distinct time evolutions. We can relate the development of these regions and the behavior of the contact line to the evolution of surface energies in the system. Additionally, we can relate the formation of these types of assemblies to the changes in the dendritic spreading behavior observed for a weakly adsorbing surfactant. This study enables us to specify molecular-scale mechanisms governing the wetting and spreading behavior of surfactant solutions.