Determination of Surface Dilational Viscosity Using the Oscillating Bubble Method

A study of kinetic molecular exchange processes in the medium frequency range by surface SHG on an oscillating bubble

“…Several models that describe the dynamic behavior of fluid surfaces are established. But experiments in the medium frequency range, e.g., with the oscillating bubble method, exhibit discrepancies to the theoretical models [8][9][10][11]. The reason is probably the assumptions about the structure of the adsorption layer under dynamic conditions.…”

“…(4) but on its parameters. The results of the oscillating bubble experiments hint to the introduction of the proposed modified definition of the effective surface concentration described by Γ because the difference between the concentration Γ and Γ can explain the discrepancy between the calculated and measured parameters of the established LvdT model [11]. The calculation of the parameters on the basis of the isotherm equation remains only correct if Γ * is negligible.…”

“…However, near the CMC or the solubility limit the calculated parameters become unrealistically great, regardless of the approximation model and at least in this range the difference between ε m (c s ) and ε g (c s ), respectively ω m (c s ) and ω g (c s ), must be considered as verified. The comparison of experimental and calculated parameters was discussed in our previous articles in detail [9,11]. It leads to the conclusion that for the explanation of the results in critical concentration ranges additional, independent experiments are required.…”

“…(4) can be very well fitted to these experimental results, but, in the low concentration range, the experimental Gibbs elasticity, ε m (c s ), is larger than ε g (c s ) whereas for higher concentration near the CMC or the solution limit, ε m (c s ) and ω m (c s ) have too small values. These effects are very often verified by surface rheological measurements with the oscillating bubble method [9,11]. The method allows the determination of the modulus up to a magnitude of 150 mN/m in the frequency range 1 f 500 Hz.…”

“…It is introduced for formal reasons to characterize the influence of dissipative losses within the surface layer on the surface tension. Experimental results request this term [8][9][10][11][12][13][14]. Here we consider only the compositional effects because the solution used shows no influence of an intrinsic surface dilatational viscosity (κ = 0).…”