Abstract:

This article is the first part of a two-part study that exemplifies how to treat the solubilization of water in multicomponent surfactant-based systems. In particular, it aims at clarifying the role of cosurfactants in water solubilization in these systems. The judicious selection of the components in such systems to maximize water solubilization is occasionally thought to be dictated by the chain length compatibility principle, which may be expressed quant. by the BSO (Bansal, Shah, O'Connell) equation. Here we demonstrate some limitations of the equation. For example, in our best model system, C12(EO)8/dodecane + pentanol = 1:1 (by wt.)/water at 27 ± 0.2 ° C, the BSO equation predicts that no alc. is needed for max. water solubilization, contrary to our exptl. findings. We discuss how to optimize the alc./oil wt. ratio needed for stabilizing four-component microemulsions. In our model systems C12(EO)8 or C18:1(EO)10/pentanol/dodecane/water, this optimal wt. ratio is 1:1. We also highlight the difference between the effect of normal alcs. on water solubilization-which passes via a max.-and their effect on percolation processes and structured changes of proteins, which depends solely upon the alc. hydrophobicity. For the investigation of the effect of branching on phase behavior the utilization of an extended form of the geometrical branching factor F b is suggested. The meaning of this factor is elucidated by comparing it with topol. indexes. [on SciFinder(R)]