Surface Activity and Efficiency of Cat-Anionic Surfactant Mixtures

Abstract

The surface activity of surfactant mixtures is critically analyzed. Cat-anionic systems, in which two ionic species are mixed in non-stoichiometric ratios, are considered. With respect to the solution behavior, where a substantial decrease of cmc is met compared to the pure components, a moderate effect on surface tension, γ, occurs. Compared to the pure species, the decrease of surface tension for such mixtures is not significant, and no clear dependence on the mole fraction anionic/cationic is met. The surface tension is grossly constant in the whole concentration range. Conversely, the interaction parameter for surfaces, βsurf (calculated by the regular solution theory), is more negative than that for micelle formation, βmic. This fact suggests that the desolvation of polar heads of the two species at interfaces is largely different. Very presumably, the underlying rationale finds origin in the sizes and solvation of both polar head groups.

Surfactant mixtures: A short review

“…As might be expected, there are a number of texts on surfactant mixtures (Abe & Scamehorn, 2005; Holland & Rubingh, 1992; Ogino & Abe, 1993; Scamehorn, 1986a), although none are recent and all are edited texts which means that the texts are less likely to be 100% comprehensive. A number of review articles on surfactant mixtures have been written as well (Khan & Marques, 1999; Kronberg, 1997; La Mesa & Risuleo, 2021; Smirnova, 2005; Sugihara et al, 2008) but almost all of these, as well as others in the literature, are focused on a specific type of mixture (e.g., mixtures of cationic and anionics) or a specific phenomenon (e.g., micelle formation). Some specific phenomena are much better reviewed (and studied) than others; for example, there have been many papers on mixed micelle formation while much less has been done on either adsorption at the solid–liquid interface, or precipitation.…”