Surfactants three-component phase diagram

The sulfones, sulfolane and 3-methylsulfolane, are shown to function quite well, as cosurfactants with CTAB, in the solubilization of both organophosphorus esters and betahalosulfides. For the organophosphate used, tributylphosphate, it is shown through pseudo-three-component phase diagrams that the sulfone functions as effectively as the alcohol in its role of cosurfactant. Solubilization of chloroethyl ethyl sulfide is less effective when the sulfone cosurfactant is used, but is still a dramatic enhancement over its solubility in water alone. The effect of added salt on the solubilization is reported, as well as the effect of changes in the surfactant-cosurfactant ratio. Preliminary quasielastic lightscattering measurements are also reported for these unconventional systems. 

From the phase behavior of both binary mixtures (water-amphiphile and oil— amphiphile), it is now possible to account, at least qualitatively, for the three-component phase diagram as a function of temperature. The presence of a haze point on the oil-amphiphile phase diagram (critical point a) at temperature Ta shows that the surfactant is more compatible with the oil at high than at low temperature. The presence of a cloud point on the water-amphiphile phase diagram (the lower critical point (>) at temperature Tjj shows that (at least in the neighborhood of the temperature domain) the amphiphile is less compatible with water at high than at low temperature. As a consequence (the other parameters being kept constant), the amphiphile behavior depends on temperature. 

Figure 20 A schematic representation of a three-component phase diagram for a surfactant-oil-water system. (From Ref. 36.)...

A large variety of structures is encountered when the three-component phase diagram is traversed (Fig. 3). At the lowest surfactant concentrations, aggregations of the surfactant into single spherical micelles can be found. As the concentration is increased these micelles become elongated and then form an infinite cylinder, due to the periodic boundary conditions. This regime and its... 

Diethylene glycol monoalkyl ether was used as a cosurfactant in the formation of an oil-in-water styrene microemulsion. Sodium dodecyl sulphate was used as a surfactant. The pseudo three-component phase diagram, macroemulsion, microemulsion and lamellar gal phases, was constructed for the cosurfactants. A smaller number of latex particles nucleated than there were microemulsion droplets initially present. The diethylene glycol monoalkyl ether group of CiEj enhances the latex stability and the CiEj more effectively stabihses the styrene microemulsion and subsequent polymerisation compared with CiOH cosurfactants used as a comparison. 15 refs. 

Figure 1 shows a schematic representation of the pseudo three-component phase diagram of a surfactant/cosurfactant-oil-water system. Depending on formulas, fine oil droplets dispersed in the continuous aqueous phase [0/W (or direct) microemulsion] or fine water droplets dispersed in the continuous oily... 

Figure 6.1 shows a schematic representation of the pseudo three-component phase diagram of a typical (surfactant/cosurfactant)-oil-water system. Depending on formulas, fine oil droplets dispersed in the continuous aqueous phase [O/W (or direct) microemulsion] or water droplets in the continuous oily phase [W/O (or inverse) microemulsion] are obtained. Furthermore, the intermediate region between the OAV microemulsion phase and the W/O microemulsion phase is characterized by a bicontinuous microstructure in which the aqueous and oily microdomains are interconnected with each other [13, 14]. The presence of such a middle phase in the colloidal system was verified by literature data [15]. It was shown that the oil-water interfacial layer in the bicontinuous microstructure has a zero mean curvature (i.e., it is flat on the average), and this sponge-like microstructure is completely disor-... 

CMC-temperature curves of each component. By analogy with the two-component phase diagram, we can conclude from this three-component phase diagram that the rational Krafft point for a binary surfactant mixture is determined by the intersection of the mixed CMC surface with both humped surfaces of the surfactant solids. 

The effect of additives on mesophases of fluorinated surfactants has been studied by Tiddy and Wheeler [ 163] and Rosenblatt [176]. Tiddy and Wheeler described the effects of -octanol on the ammonium perfluorooctanoate-water system with a three-component phase diagram (Fig. 7.39). The main differences between phase diagrams for this system and that for sodium octanoate- octanol-water were related to mutual phobicity between fluorocarbon and hydrocarbon chains. Octanol was found to be less soluble in the aqueous micellar phase of ammonium perfluorooctanoate than that of sodium octanoate. However, ammonium perfluorooctanoate is more soluble in octanol than sodium octanoate. This solubility difference is probably related to the effect of counterions, as ammonium salts are usually more soluble in octanol than sodium salts. 

Figure 6.4. Schematic phase diagram for a three-component (oil, water, surfactant) system showing some of the self-assembled structures which form in the various regions.

In 1959, J. H. Schulman introduced the term microemulsion for transparent-solutions of a model four-component system [126]. Basically, microemulsions consist of water, an oily component, surfactant, and co-surfactant. A three phase diagram illustrating the area of existence of microemulsions is presented in Fig. 6 [24]. The phase equilibria, structures, applications, and chemical reactions of microemulsion have been reviewed by Sjoblom et al. [127]. In contrast to macroemulsions, microemulsions are optically transparent, isotropic, and thermodynamically stable [128, 129]. Microemulsions have been subject of various... 

We saw in Section 8.6 that phase diagrams are an effective way of representing the complex behavior of surfactant systems. Let us take a look at microemulsions in terms of phase diagrams. It turns out that nonionic surfactants form microemulsions at certain temperatures without requiring cosurfactants. Since only three components are present, these have somewhat simpler phase diagrams this kind of system offers a convenient place to begin. 

FIGURE 2 Ternary phase diagram used to elucidate ME formation regions. Each of the three corners represents 100% of the individual components. Apex S = 100% w/w surfactant (0% oil and water), apex W = 100% w/w water (0% oil and surfactant), and apex O = 100% w/ w oil (0% water and surfactant). The three lines joining the corner points represent two-component systems. The area within the triangle represents all possible combinations of the three components. 

Consider the phase diagram of a three-component system of water, ionic surfactant and medium-chain alcohol, as described in Figure 15.4. At the water comer... 

Figure 14 Self-diffusion coefficients of surfactant, water, and oil in a three-component microemulsion (L2) phase with AOT, water, and /j-xylene. The samples are labeled from 1 to 18, and the compositions are indicated in the phase diagram. Note the very similar diffusion coefficients of water and AOT over the full concentration range, showing that the structure is made up of discrete reverse micellar aggregates. The fact that the diffusion coefficient of the oil is high everywhere confirms that the structure is oil-continuous. (Data taken from Ref. 94.)...

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