Investigating the effect of interfacial hydrogen bonding on the surface mobility and foam drainage kinetics

The foam drainage presents a fascinating science and important applications. This phenomenon is complex and governed by multiscale interaction which is not fully understood. Here, we use combined experimental methods based on forced foam drainage, dynamic surface tension measurements and interface-susceptible sum frequency generation spectroscopy to investigate the effects of glycerol and methyl isobutyl carbinol (MIBC) on the forced drainage of a foam formed by sodium dodecyl sulfate (SDS). We observed opposite effects of glycerol and MIBC on foam drainage kinetics. MIBC slows down the foam drainage while glycerol surprisingly accelerates this process. The unexpected effect of glycerol is attributed to its capability of forming hydrogen bonding with interfacial water, which leads to a strong disruption of the interfacial hydrogen bonding between SDS and water in the topmost layer. Ultimately, this effect leads to increased surface mobility and accelerated foam drainage. In contrast, MIBC reduces the foam drainage rate by decreasing surface shear viscosity and inducing a Marangoni effect due to increasing surface tension. Hence, we experimentally demonstrate the crucial role of interfacial hydrogen bonding between surfactant and water as a determining factor of the foam drainage velocity, thereby, providing a molecular-level understanding of foam drainage kinetics.