(570b) Effect of Pressure On Micelle Aggregation and Solubilization

In deep sea application of dispersants, pressure can have a significant effect on their self-assembly properties and oil solubilization. We have undertaken a molecular simulation study to piece apart the molecular-level contributions to pressure induced micellar aggregation. The effect of pressure on the partial molar volumes  in aqueous solution were investigated for three different surfactants including the anionic surfactant sodium decyl sulfate, the cationic surfactant decyl trimethyl ammonium bromide, and non-ionic surfactant penta ethylene glycol monodecyl ether. The partial molar volumes of surfactants in micellar and monomeric dispersed states have been simulated in the pressure range of 1-2500 bar. The partial molar volume change on micelle formation transforms from a positive value to a negative value as the pressure increases, which corresponds to the observed maximum value in the critical micelle concentration vs pressure curve. The tail group of the surfactant contributes most to the partial molar volume change has been demonstrated using Kirkwood-Buff theory. The effects of pressure on micelle solubilization of non polar gases is also discussed.