Molecular Interactions and Synergism in Mixtures of Two Surfactants

In most practical applications, mixtures of surfactants, rather than individual surfactants, are used. In some cases, this is involuntary, since the commercial surfactants used, even when designated by the name of an individual surfactant, e.g., sodium lauryl sulfate, are mixtures of surface-active materials as a result of the nonhomogeneous raw materials used in their manufacture and/or the presence of unreacted raw materials and manufactured by-products. In other cases, different types of surfactants are purposely mixed to improve the properties of the final product. 

In most cases, when different types of surfactants are purposely mixed, what is sought is synergism, the condition in which the properties of the mixture are better than those attainable with the individual components by themselves. For example, a long-chain amine oxide is often added to a formulation based upon an anionic surfactant because the foaming properties of the mixture are better than those of either surfactant by itself. 

Surfactants and Interfacial Phenomena, Third Edition. Milton J. Rosen ISBN 0-471-47818-0 2004 John Wiley Sons, Inc. 

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