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Surfactant Structure and the Solubilization Process

Earlier chapters introduced some of the wide array of chemical species that exhibit surfactant properties and are potentially useful in solubilization processes. Just as molecular structure is important to such surfactant characteristics as the cmc, aggregation number, and micellar shape, it also controls the ability of a surfactant to solubilize a third component. Conversely, the presence of a third component in a surfactant solution can often affect its aggregation characteristics. It is documented in a number of reports that the presence of a solubilized additive, even though the additive has no inherent surface activity, can change the cmc of a surfactant substantially from that of the pure system. As noted in Chapter 4, the existence of such an effect means that great care must be exercised in the interpretation of experimental data on micellization derived from solubilization results. [Pg.196]

Whether micelles formed in the presence of a third component are the same as those formed in its absence is a subject of some controversy. It has been shown that micellar activity may be induced in surfactant solutions below the normal cmc in the presence of small amounts of solubilized additives. In some cases such effects have been attributed to additive-induced micellization. In others, effects have been seen at concentrations several orders of magnitude below the cmc, suggesting the presence in solution of submiceUar species possessing some properties of the fully aggregated system. [Pg.196]

Since the erne s of most surfactants occur at rather low concentrations, evidence of premicellar aggregate formation quite often becomes a question of the interpretation of results lying at the limits of sensitivity and accuracy of many experimental techniques, and, of course, the view of the individual interpreter of those results. There seems to be little doubt that in nonaqueous solvents, the formation of dimer and other lower aggregates occurs readily. Fluorescence and electron spin resonance techniques have also shown the presence of such species in very bulky surfactant systems in water. However, there is presently littie unambiguous [Pg.196]

In a study of the solubilization of ethylbenzene in a series of potassium carbox-ylates ranging from Cg to Cig, it was found that as the concentration of surfactant increased, the amount of ethylbenzene solubilized increased, and that as the length of the carbon chain increased, the quantity of material incorporated per mole of surfactant increased with the carbon chain length. Such results have been criticized because of the assumption that the activity of the monomeric surfactant remained [Pg.197]

TABLE 6.1. Effects of Surfactant Hydrocarbon Chain Length on cmc and Solnbilization of Ethylbenzene in Potassium Soap Solutions  [Pg.197]


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