Abstract
Hexanol is used as a cosurfactant in a wide variety of consumer products and industries manufacturing surfactant based formulations. Surfactants present in these products adsorb at interfaces and cause interfacial tension driven Marangoni flows. Presence of a medium chain alcohol additive in conjunction with the surfactant is expected to effect the Marangoni driven flow at the liquid/liquid interface. Alcohol molecules are surface active, they not only compete with the surfactant to adsorb at the interface, but also are incorporated into the surfactant micelles at concentrations greater than the CMC, thus changing the micellar size and shape. This work shows the effect of hexanol on the sodium dodecyl sulfate driven Marangoni transport at the oil/water interface. Interfacial particle trajectories are recorded using optical microscopy. Presence of hexanol along with SDS is found to increase the peak Marangoni velocity of the interfacially adsorbed microparticles at concentrations both above and below the CMC during the adsorption stage. An increase in the displacement during the adsorption stage is also observed. This is only significant as low SDS concentrations. At the higher SDS concentrations tested in this study, the displacement for the multi-component SDS and hexanol system is not found to be statistically different from the single-component SDS system. Hexanol can be used to alter the lag time for Marangoni flow in the desorption stage since it lowers the CMC of the surfactant solutions.
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