Negative synergism

In many products or processes, two surfactants are used together to improve the properties of the system. In some cases, the two surfactants interact in such fashion that the CMC of the mixture (Cf2) is always intermediate in value between those of the two components Cf, C2). In other cases they interact in such fashion that Cf2 at some ratio of the two surfactants is less than either Cf1 or C2. When the latter case occurs, the system is said to exhibit synergism in mixed micelle formation. In still other cases, Cf2 at some ratio of the two surfactants may be larger than either Cf or C2. Here the system is said to exhibit antagonism (negative synergism) in mixed micelle formation. 

III.A. Synergism or Antagonism (Negative Synergism) in Surface or Interfacial Tension Reduction Efficiency... 

From the relations upon which equations 11.1 and 11.2 are based and the definition for synergism or antagonism (negative synergism) of this type, it has been shown mathematically (Hua, 1982b, 1988) that the conditions for synergism or antagonism, in surface tension reduction efficiency to exist are ... 

A single surfactant may satisfy all three roles, or there may be a requirement for multiple surfactants. The optimum choice of surfactant for one role may produce undesirable performance in other roles, and there may be positive or negative synergism exhibited when multiple surfactants are used. As with many other aspects of emulsion polymerization, a compromise is often required in the choice of surfactant. 

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