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The desorption of C 12 E 8 out of an overcrowded interface due to the sudden shrinkage of a pendant bubble in a quiescent surfactant solution is studied. A video-enhanced pendant bubble tensiometry is utilized for the measurement of the relaxation in surface tension due to the desorption of surfactant. The desorption process is found to be diffusive-kinetic mixed controlled. Rate constants of adsorption/desorption are computed by comparing these tension profiles with numerical solutions, which consider both bulk diffusion and kinetic desorption processes. The values of the kinetic rate constants of C 12 E 8 obtained from the desorption experiment are nearly the same as that obtained from the clean adsorption study (Lin, S. Y., et al., Langmuir 1996, 12, 6530). The concept that there exists a shift in controlling mechanism from diffusion control at dilute concentration to mixed diffusion-kinetic control at more elevated bulk concentration for C 12 E 8 is therefore confirmed.

The adsorption of C12E4 onto a fresh air−water interface was investigated by using video-enhanced pendant bubble tensiometry. From the comparison between the equilibrium surface tension data and the theoretical relaxation profiles predicted by the Frumkin adsorption isotherm, the adsorption process was found to be anticooperative. Dynamic surface tension data for C12E4 molecules absorbing onto a freshly created air−water interface for different bulk concentrations were used for the determination of the controlling mechanism and the evaluation of diffusivity. Comparison was made for the entire relaxation period of the surface tension data and the model predictions. It is concluded that the adsorption process is of diffusion control and the diffusion coefficient is 6.4 × 10-6 cm2/s. The lower limit of the adsorption rate constant of C12E4 were obtained from the theoretical simulation. Besides, the pendant bubble, at which the interface had reached the equilibrium state, was expanded rapidly and a relationsh...