Dr. Marie-Esther Saint Victor
Manager, Applied Physics Group
Discussion and Special Interests Group
ACS, Surface Science and Colloid Division
December 7, 2000
Abstract: Strong synergistic
interactions are usually observed in surfactant mixtures comprising
Alkylpolyglycoside (APG®)
and nonionic surfactants. Both solution
and interfacial properties of the mixtures are significantly enhanced, compared
to the properties of the individual surfactants. Moreover, APG® surfactants tend to
increase the cloud points of nonionic surfactants.
Four major forces contribute to
these interactions: (1) contribution from the break-up of the structure of water molecules as the temperature increases; (2)
surfactant-water compatibility or antipathy; (3) self-association of surfactant
molecules in solution; and (4) surfactant-surfactant interactions. The synergistic
interactions in these mixtures exhibit strong temperature and concentration dependence. A “local composition Non-Randomness”
causes a concentration-concentration
fluctuation in the middle of the concentration range.
In an effort to model these interactions, excess thermodynamic properties of mixtures comprising APG® as a co-surfactant were systematically investigated. The interactions are “non-ideal” and exhibit a strong deviation from the predictions of the Flory-Huggins Regular Solution Theory. The properties and efficiency of mixtures of APG® with various ethoxylated surfactants are reviewed.