Surfactant anionic-cationic mixture

Fig. 15 CMC of anionic-cationic surfactant mixtures as a function of composition of the mixture...

The phase behavior of anionic-cationic surfactant mixture/alcohol/oil/ water systems exhibit a similar effect. First of all, it should be mentioned that because of the low solubility of the catanionic compound, it tends to precipitate in absence of co-surfactant, such as a short alcohol. When a small amount of cationic surfactant is added to a SOW system containing an anionic surfactant and alcohol (A), three-phase behavior is exhibited at the proper formulation, and the effect of the added cationic surfactant may be deduced from the variation of the optimum salinity (S ) for three-phase behavior as in Figs. 5-6 plots. Figure 16 (left) shows that when some cationic surfactant is added to a SOWA system containing mostly an anionic surfactant, the value of In S decreases strongly, which is an indication of a reduction in hydrophilicity of the surfactant mixture. The same happens when a small amount of anionic surfactant is added to a SOWA system containing mostly a cationic surfactant. As seen in Fig. 16 (left), the values of In S at which the parent anionic and cationic surfactant systems exhibit three-phase behavior are quite high, which means that both base surfactants, e.g., dodecyl sulfate... 

Upadhyaya A, Acosta EJ, Scamehorn JF, Sabatini DA (2006) Microemulsion phase behavior of anionic-cationic surfactant mixtures Effet of tail branching. J Surfact Deterg 9 169-179... 

Except for some anionic/cationic surfactant mixtures which form ion pairs, in a typical surfactant solution, the concentration of the surfactant components as monomeric species is so dilute that no significant interactions between surfactant monomers occur. Therefore, the monomer—mi celle equilibria is dictated by the tendency of the surfactant components to form micelles and the interaction between surfactants in the micelle. Prediction of monomer—micelle equilibria reduces to modeling of the thermodynamics of mixed micelle formation. 

Anionic/Cationic Surfactant Mixtures. Mixed micelles... 

Synergy with anionic-cationic surfactant mixtures... 

The synergisms of mixtures of anionic-cationic surfactant systems can be used to form middle-phase micro emulsions without adding short-chain alcohols [109, 110]. The surfactants studied were sodium dihexyl sulphosuccinate and benzethonium chloride. The amount of sodium chloride required for the middle-phase microemulsion decreased dramatically as an equimolar anionic-cationic surfactant mixture was approached. Under optimum middle-phase microemulsion conditions, mixed anionic-cationic surfactant systems solubilised more oil than the anionic surfactant alone. Upadhyaya et al. [109] proposed a model for the interaction of branched-tail surfactants (Fig. 8.16). According to this model the anionic-cationic pair allows oil to penetrate between surfactant tails and increases the oil solubilisation capacity of the surfactant aggregate. Detergency studies were conducted to test the capacity of these mixed surfactant systems to remove oil from... 

Figure 8.16 Schematic drawing of the surfactant layer and oil penetration in anionic-cationic surfactant mixtures where (a) both surfactants have linear tails, (b) one surfactant has a linear and one a branched tail and (c) both surfactants have branched tails. (From Ref. [109], reprinted with permission of AOCS.)...

V. MICROEMULSIONS WITH ANIONIC-CATIONIC SURFACTANT MIXTURES... 

As explained in detail elsewhere [99], it seems that the anionic-cationic surfactant mixtures would contain a certain amount of catanionic equimolecular compound, which is much less hydrophilic than its components, and an excess of either the anionic or cationic surfactant. In other words, a mixture containing 10 mol of cationic surfactant and 90 mol of anionic surfactant would really behave as a mixture of 80 mol of anionic surfactant with 10 mol of the catanionic equimolar component. There is evidence that this anionic-cationic... 

Anionic-cationic surfactant mixtures make the potential of the bubble close to zero over the wide mid-range composition, where the critical micelle concentration corresponds to the catanionic species. 

The cloud point temperature of the anionic-cationic surfactant mixtures is affected by the total surfactant concentration and by the relative concentration of the anionic and cationic surfactants. Solutions with excess anionic surfactant showed one minimum in their cloud point temperature versus total surfactant concentration graph (Fig. 10). The cloud point temperature of the minimum increased with an increase in the anionic surfactant mole... 

Kume, G., Gallotti, M. and Nunes, G. (2008) Review on anionic/cationic surfactant mixtures. J. Surfactants Deterg., 11, 1-11. 

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