Adsorption layer characteristics of Triton surfactants: 4. Dynamic surface tension and dilational visco-elasticity of micellar solutions

The presence of micelles in the solution accelerates the adsorption dynamics of Tritons at the solution/air interface, depending on the micelle dissolution rate. Micellar solutions (at CMC and up to about 10× CMC) are studied by maximum bubble pressure tensiometry and oscillating bubble profile tensiometry. The dynamic surface tensions in the time range between 0.1 ms up to 50 s are analysed by a diffusion controlled mechanism. At very short times the effect of molecular reorientation of the Triton molecules at the surface is observed. The dilational elasticity data at low frequencies (0.005–0.2 Hz) provide good agreement with a respective model assuming a very fast micelle dissolution. While for Triton X-45 and X-100 a quantitative agreement with existing theories is observed, the results for Triton X-165 and X-405 agree only qualitatively. This discrepancy is obviously due to the respective composition of the technical surfactants and a quantitative understanding would require an accurate knowledge on the sample composition.