Influence of Surface Tension on Adsorbate Molecular Rotation at Liquid/Liquid Interfaces

Molecular dynamics computer simulations of a series of liquid/liquid interfaces with variable surface tension and fixed bulk viscosity are used to study the effect of the liquid surface on the rotational correlation time of a molecular solute adsorbed at the interface. We observe a remarkable attenuating effect on the rotational dynamics as the surface tension is reduced and show that the origin of the effect is a local density gap. This gives rise to a local effective viscosity, which increases as the surface tension is decreased.