Nonequilibrium properties of fluid interfaces: aperiodic diffusion-controlled regime. 2. Experiments

摘要

We have investigated the surface dilational properties of a submicellar aqueous solution of n-dodecyldimethyl-phosphine oxide. We compared (a) the steady-state responses of dynamic surface tension, induced by small-amplitude harmonic disturbances of surface equilibrium (at different frequencies), and (b) the transient response induced on the same sample by a single trapezoidal-pulse disturbance. Using the equations for a diffusive model, we determined the fit parameters from the observed response values both in the frequency and in the time domains. The results enabled us to predict satisfactorily the harmonic dynamic behaviour of the surface, from the relaxation data. The prediction-observation agreement supports the theoretical treatment and, in particular, the assertion that the viscoelastic link, between surface excitation and response, is a constitutive property of a liquid solution. The experiments also show the existence of a linearity range and the repeatability of measurements.