Solubilization-Site-Dependent Micellar Morphology: Effect of Organic Additives and Quaternary Ammonium Bromides

Abstract

Here we report systematic viscosity measurements under Newtonian flow conditions for sodium dodecyl sulfate (SDS) micellar solutions in the presence of aliphatic hydrocarbons (n-hexane, n-heptane, n-octane), toluene, and 1-alkanols (1-heptanol, 1-octanol) at 30 °C. The influence of 0.1 M quaternary ammonium bromides (R4NBr; R = H, CH3, C2H5, n-C3H7, n-C4H9, n-C5H11) was seen on relative viscosity (ηr) vs additive concentration profiles. Lower members of R4NBr (R = H, CH3, C2H5) have marginal influence on viscosity profiles and hence on micellar morphology. This may be due to the less pronounced effect on association structures as well as on solubilization sites (and on solubilizate content at a particular site) of added organics. As the alkyl part of R4NBr was increased (R ≥ n-C3H7), the effect, which depended upon the nature of the additive (i.e., its hydrophobic/polarity character), was significant. This is possibly due to salts affecting the partitioning content of organic additives at different micell...