ABSTRACT
The field of applications of surfactants is immense. So many of the products used in every day life contain surfactants: prepared foods, personal care products, drugs, soaps, paints, detergent formulations for dishwashers and washing machines, and so forth. The formulations of these products are usually based on mixtures of surfactants. This may due to the fact that the synthesis of the surfactants present in formulations uses starting materials that are not chemically pure and that may show in the case of nonionic surfactants, for instance, some variability in the length of the poly(ethylene oxide) group. This may also result from the deliberate will of the formulator, who, by mixing surfactants, tries to give the mixture improved properties with respect to those of the isolated surfactants (synergism) or even new properties. It is therefore not surprising that mixed-surfactant systems are attracting considerable interest both in academic and industrial laboratories. The number of articles published every year on mixed-surfactant systems is very large. Two recent volumes have reviewed many aspects of this field [1,2].
