Surfactant Self-Assemblies Controlling Spontaneous Dewetting

We have examined the structures of surfactant self-assemblies left on substrates as a contact line spontaneously retreats across the surface during an autophobing event. A continuous structural gradient is formed during the spontaneous retreat: from molecules lying down on the surface with low packing densities in a region never touched by the solution, to molecules standing up with higher packing densities in a region where the contact line has moved slowly. Despite significant free volumes within the self-assemblies, there is no evidence of clustering of molecules. We have observed a clear correlation between retreating contact line speeds and deposited surfactant structures. The dynamics during at least a later period of the autophobing event is dominated by the time evolution of Young's force dictated by the self-assembly near the contact line.