PRE Scientist Supplement: Molecular Interactions in Binary Mixtures of Surfactants

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Research Summary: This is an investigation of conditions under which mixtures of two surfactants exhibit synergism, i.e., show properties that are better than those of the individual surfactants by themselves. There are three foci of the research: (1) Synergism is dynamic surface tension. Here the principal investigator is investigating the rate at which surface tensions are reduced. (2) Negative synergism. This is a novel phenomenon recently observed where the mixture demonstrates an interfacial property to a smaller extent than the individual surfactants by themselves under similar conditions. (3) New equations for calculating the molecular interaction parameters that are the basis for synergism. Synergism is investigated by measuring various interfacial properties (surface and interfacial tension, contact angle, foaming) of the individual surfactants and their mixtures. Dynamic surface tension will be investigated with their new apparatus. Significance. Surfactants, which are used in a vast number of industrial processes and consumer items, are generally mixtures containing at least two surface-active components. This research will provide guidelines for the selection of surfactant pairs that can optimize their performance in those products and processes. From the relevant properties of the individual surfactants by themselves and the value of an easily-measured interaction parameter, this treatment allows one to predict: (1) whether a synergistic interaction will occur when two surfactants are mixed and, if so, (2) the ratio of the two that will show maximum synergism, and (3) the properties of the system at that point. This means that we now have a powerful, new tool for improving performance in a multitude of industrial processes and products.