Aqueous Mixtures Of Sodium Dodecyl Sulfate Research Articles

A parameter predict ing the foam stability of mixtures of aqueous ionic amphiphile solutions with indifferent electrolyte

Sodium dodecyl sulfate (SDS) is a well-defined model substance for anionic molecular surfactants. Aqueous mixtures of SDS in a surface chemically purified state and high purity NaCl were studied with respect to their equilibrium and dynamic surface tensions at a constant mean ionic activity Imean of 1mmolL−1. All studied solutions possessed the same equilibrium surface tension, however they showed striking differences in foam column and foam lamella stability experiments. This observation suggested the interpretation of the results in terms of dynamic interfacial properties. Oscillating bubble experiments were conducted to determine the frequency dependence of the surface dilatational modulus in a range from 5 to 400Hz. The obtained surface dilatational modulus could be described by the extended Lucassen-van den Tempel (LvdT) model, which allows capturing dissipative processes by the intrinsic surface viscosity κ within the interfacial region. A new parameter derived from the fitting parameters of the LvdT model correlates reasonably with direct measurements of the solutions’ foam stability. The data suggest the important role of surface rheology for the stability of foams.

The Properties of Mixtures of Sodium Dodecylsulfate and Diethylsulfoxide in Water

The aqueous mixtures of sodium dodecylsulfate (SDS) and diethylsulfoxide (DESO) have been studied using conductivity, viscosity and surface tension techniques. The critical micellar concentration (cmc) was determined in the presence of DESO at 30, 40, and 50 ∘C from conductance and surface tension measurements. The enthalpy (Δ Gm∘), entropy (Δ Sm∘) and Gibbs energy (Δ Gm∘) of micellization were determined from the temperature dependence of the cmc. The results obtained were compared with published results for aqueous solutions of SDS and dimethylsulfoxide (DMSO). The data demonstrate a more pronounced inhibitory effect of DESO on the micellization of SDS, in comparison with the effect of DMSO. On the basis of the dependences of the relative viscosities on concentration, as given by the Jones–Dole semi-empirical equation, the B-coefficients have been calculated for the post-micelle composition region.

Interaction between Poly(ethylene oxide) and Sodium Dodecyl Sulfate Studied by Neutron Reflection

The composition of the air/solution interface of aqueous mixtures of sodiumdodecyl sulfate (NaDS) and poly(ethylene oxide) (PEO) has been studied as a function of NaDS concentration and at a fixed concentration of 0.1 wt % PEO using neutron specular reflection. With increasing surfactant concentration, the polymer is progressively displaced from the surface until, at the critical aggregation concentration (CAC), it can no longer be detected (area per segment greater than about 80 Å2. The adsorption of surfactant increases steadily with concentration and shows no sign of a discontinuity at the CAC (4.5 mM at 35 °C), which is consistent with the break in the surface tension curve being caused only by the onset of surfactant/polymer aggregation in the bulk solution. At all concentrations the adsorption of NaDS at the air/solution interface is less in the presence of polymer than that in the corresponding solutions without polymer. Nevertheless, it is shown that there is some cooperativity in the adsorption of polymer and surfactant at the interface.