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Molecular-Thermodynamic Theory of Micellization of Multicomponent Surfactant Mixtures: 1. Conventional (pH-Insensitive) Surfactants
journal contribution
posted on 2007-05-22, 00:00 authored by Arthur Goldsipe, Daniel BlankschteinA molecular-thermodynamic (MT) theory was developed to model the micellization of mixtures containing an
arbitrary number of conventional (pH-insensitive) surfactants. The theory was validated by comparing predicted and
experimental cmc's of ternary surfactant mixtures, yielding results that were comparable to, and sometimes better than,
the cmc's determined using regular solution theory. The theory was also used to model a commercial nonionic
surfactant (Genapol UD-079), which was modeled as a mixture of 16 surfactant components. The predicted cmc agreed
well with the experimental cmc, and the monomer concentration was predicted to increase significantly above the
cmc. In addition, the monomer and the micelle compositions were predicted to vary significantly with surfactant
concentration. These composition variations were rationalized in terms of competing steric and entropic effects and
a micelle shape transition near the cmc. To understand the packing constraints imposed on ternary surfactant mixtures
better, the maximum micelle radius was also examined theoretically. The MT theory presented here represents the
first molecular-based theory of the micellization behavior of mixtures of three or more conventional surfactants. In
article 2 of this series, the MT theory will be extended to model the micellization of mixtures of conventional and
pH-sensitive surfactants.