Eco-solvents – cluster-formation, surfactantless microemulsions and facilitated hydrotropy

In this paper we consider clusters in the ternary systems water-benzyl alcohol and ethanol, ethyl lactate or γ-valerolactone as found with the help of dynamic and static light scattering experiments. These ternary mixtures are powerful solvent media and consist only of low-toxic solvents of natural origin. In a recent work we have shown that surfactantless microemulsions are formed in the water-ethanol-n-octanol system. By contrast, in the systems studied here the sizes of the aggregates are too small to be considered as micelles. It can be postulated that the presence of clusters or larger structures as in surfactantless microemulsions is strongly influenced by the most hydrophobic compound. The phenomenon of facilitated hydrotropy is also investigated in the above-mentioned systems. In this context, ethanol is considered as the primary hydrotrope and the more hydrophobic benzyl alcohol as the facilitating secondary hydrotrope. The hydrophobic dye Disperse Red 13 is used as a marker of facilitated hydrotropy. The results suggest that the degree of self-association of eco-solvent has a significant influence on the hydrotropic efficiency of benzyl alcohol.