Abstract
We proposed an experiment which can be used to test if bulk diffusion is the controlling mechanism for surfactant adsorption at an air/liquid interface. This method involves the measurements of the dynamic surfactant tension Pi (t) and the high-frequency surface elastic modules epsilon sub(0)(t), as a function of time, for a newly created fresh interface. A key feature of the proposed approach is that it does not require information on the surfactant bulk diffusion coefficient and the use of a surface equation of state. It is shown that the quantity t epsilon sub(0) super(-1) d Pi /dt must be equal to 0.5 for diffusion-controlled adsorption. This test was used to investigate the adsorption of two nonionic surfactants, C12E6 (hexaethylene glycol mono-n-dodecyl ether) and Triton-X-100).