DYNAMIC SURFACE-PROPERTIES OF AQUEOUS BRIJ58 SOLUTIONS AT THE AIR-WATER-INTERFACE

For surfactant Brij58, which exhibits the dynamic characteristic of slow diffusion-controlled adsorption at the air/water interface, the stress relaxation method was used to measure the Gibbs elastic modulus (epsilon0) and the diffusion relaxation time (tau(D)). Two other methods, the peak tensiometric method proposed recently by M. Van Uffelen and P. Joos and a strip method, were also used to obtain epsilon0square-roottau(D) as a comparison. The three methods give consistent results. A discussion is presented of the description of the dynamic parameters by the Langmuir and Freundlich isotherms which fit the equilibrium surface tension concentration curve reasonably well. The Langmuir isotherm gives erroneous results for epsilon0 and tau(D) but the correct order of magnitude for epsilon0square-roottau(D). The Freundlich isotherm can better describe epsilon0 and tau(D) but gives a poorer result for epsilon0square-roottau(D) than the Langmuir isotherm.