INPLANE STEADY SHEAR VISCOSITY OF MONOLAYERS AT THE AIR-WATER-INTERFACE AND ITS DEPENDENCE ON FREE AREA

A canal surface viscometer was used to measure the in-plane steady shear viscosity of monolayers of amphiphilic molecules at the air/water interface. Measurements were made for stearic acid, dipalmitoylphosphatidylcholine, and poly(tert-butyl methacrylate) over a range of surface mass density (or average molecular area) in the liquid-condensed phase. The mass density dependence of the surface viscosity was analyzed according to the free area model, which is a monolayer analog of the Doolittle equation for bulk systems. It also has been shown that by combining the free area relationship with the equation of state for the polymer monolayer, obtained from polymer scaling theory, one can derive the equation for the surface pressure dependence of surface shear viscosity.