Thermal-stability of mixed giant micelles of alkyltrimethylammonium surfactants and salicylate

A giant micelle changes its conformation within the flow and breaks above certain critical temperature. [Display omitted] ► Giant micelles promote hydrodynamic drag reduction (HDR). ► Thermal synergism in mixed giant micelle was investigate using such property. ► The HDR is lost if the micelles is thermally broken. ► Synergism increases if a shorter surfactant is combined with a longer. ► This is due to the better packing of the molecules that form the mixed micelles. When diluted solutions of giant micelles are under turbulent flow, large attenuations of the turbulence can be observed due to the action of the micelles on the dissipative vortices formed within the flow. This particular property is rapidly lost when the solution is heated due breakup of the giant micelles. Based on this property, we present a thermal-flow study of a mixed giant micelle formed by the combination of two surfactants and sodium salicylate. One of the surfactants, cetyltrimethylammonium bromide (C16TAB) was kept fixed, and the others were dodecyltrimethylammonium bromide (C12TAB), tetradecyltrimethylammonium bromide (C14TAB), octadecyltrimethylammonium bromide (C18TAB), polyoxyethylene (10) oleyl ether (Brij 97) or sodium dodecyl sulfate (SDS). Thermal diagrams for the combinations of the surfactants reveal deviations of the ideality. For the cationic surfactants, a synergistic effect was only observed when C16TAB was combined with the shorter surfactants.