Abstract
Adsorbed films of serum albumin, pepsin, poly-$\alpha$, L-lysine and arabinic acid of known area per residue have been formed at hydrocarbon/water interfaces. The rheology of these films was studied with an instrument capable of giving constant known shearing forces. The observed behaviour of the films has been interpreted in terms of mechanical models and the retardation spectra constructed. An examination of the origin of the viscosity and elasticity revealed the relative roles of ionic, van der Waals and hydrogen bonding. The relation between the shearing and compressional moduli of the films has been briefly discussed.