Surface Dilational Rheology of Mixed Surfactants Layers at Liquid Interfaces

Experimental data on surface tension and dilational rheology for mixtures of two non-ionic surfactants (decyl and tetradecyl dimethyl phosphine oxide) are analyzed on the basis of a recently derived model. The chosen surfactant mixtures are suitable for studies of the dilational rheology at low frequencies, as provided by slow area oscillations in drop and bubble profile analysis tensiometry. The results show that the compressibility of adsorbed layers given by the parameter has negligible effect on the equilibrium adsorption behavior but have significant influence on the frequency dependence of the viscoelasticity modulus and phase angle. The model allows also satisfactory analysis of literature data obtained for mixed anionic (sodium dodecyl sulfate) and non-ionic (dodecanol) surfactant systems.