Nonideality at the interface in mixed micellar systems

Mixed Surfactant Systems

“…In the approach developed earlier by Holland, the possibility of molar area changes arises directly in the derivation (158,159). When such changes are incorporated for anionic-cationic systems by using a simple overall ratio representing the average change in molar areas in going from the pure to mixed surfactant systems, good agreement with experimental results is seen together with a large reduction of the magnitude the surface interaction parameter j3" to near that of the micellar parameter j8.…”

“…An alternative approach which explicitly incorporates the force field term and extends the approach used for mixed micelle models to interfaces has been developed by Holland (4,158,159). Here, nonideal mixing is treated by using a form of the regular solution approximation with a surface interaction parameter j 8% but it should be noted that for a given system the magnitude of this parameter is not equivalent to that of 0° used by Rosen and co-workers (4).…”

“…This is especially pronounced in the case of anionic-cationic surfactant mixtures. The importance of explicitly considering such changes in modeling mixed surfactant systems has been increasingly recognized (4,124,126,158,159). For example, the Gibbs-Duhem relation can be used to demonstrate the importance of taking changes in the areas per molecule at the interface on mixing into account if thermodynamic consistency is to be maintained (4).…”

The Structure of the Mixed Nonionic Surfactant Monolayer of Monododecyl Triethylene Glycol and Monododecyl Octaethylene Glycol at the Air–Water Interface

“…due to the changes in distribution of the two surfactant spe- cies between the bulk solution and the monolayer as a result where r(Q) is the one-dimensional Fourier transform of r(z), the average scattering length density profile in the of the onset of mixed micelle formation at the cmc as predicted by Nikas et al (6) and the regular solution theory direction normal to the interface, (4,5). The calculations of Nikas et al (6) were for a C 12 EO 6 /C 12 EO 8 mixture, and our results for C 12 EO 3 /C 12 EO 8…”

“…Adsorp-which mix ideally and have identical alkyl chain lengths but tion and micellization in mixed surfactants have been exten-different ethylene oxide chain lengths. Rosen et al (2), in sively studied using a range of techniques, such as surface their pioneering surface tension work, extensively studied tension (2), and have been the result of considerable theoret-the adsorption of C 12 EO 3 /C 12 EO 8 mixtures at the air-water ical effort (3)(4)(5)(6). The ideal solution approach (3) and the interface.…”