Mismatch of bulk viscosity reduces interfacial diffusivity at an aqueous-oil system.

A significant decrease in the diffusivity of phospholipid molecules at an aqueous-oil monolayer was observed experimentally when the bathing solutions had different viscosities eta(1) not equal eta(2). Near the point of isoviscosity eta(1) approximately eta(2), the diffusion constant at the monolayer can be drastically affected by a slight change in the viscosity mismatch. We interpreted this phenomenon by considering the effect of vertical fluctuations which affect the long-term dynamics of two-dimensional lateral diffusion at the monolayer.