Pressure Dependence of the Critical Micelle Concentration of a Nonionic Surfactant in Water Studied by ¹H-NMR

Abstract

The critical micelle concentration (cmc) of the nonionic surfactant C8E5 in D2O was measured at 30 °C and pressures up to 350 MPa using 1H-NMR chemical shifts. The cmc was found to increase with pressure up to approximately 150 MPa and then decrease at higher pressures. This characteristic pressure dependence is similar to that reported for several ionic surfactant solutions and is in quantitative agreement with the effect of pressure on the transfer of hydrocarbons from water into nonpolar solvents. We conclude, therefore, that the observed behavior is independent of the hydrophilic headgroup of the surfactant and that it reflects a pressure-induced destabilization of the hydrophobic micelle interior at low pressures and enhanced stabilization at high pressures.

Near-infrared spectroscopic method for the sensitive and direct determination of aggregations of surfactants in various media

“…cmc values of various surfactants including CTAB, SDS, Triton X-100, Brij-35, Brij-700, Tween-20, SB-12, SB3-10 determined by this method agree very well with those determined by other methods. Because water has strong absorption in the same region as the surfactants used in this study, the cmc values were determined in D 2 O. cmc values in D 2 O are known to be different from those in water [16][17][18][19]. However, the differences are very small and in some cases can be considered to be insignificant within experimental error [16][17][18][19].…”

“…Because water has strong absorption in the same region as the surfactants used in this study, the cmc values were determined in D 2 O. cmc values in D 2 O are known to be different from those in water [16][17][18][19]. However, the differences are very small and in some cases can be considered to be insignificant within experimental error [16][17][18][19]. More importantly is the fact that the method can be used for the direct determination of cmc values of various nonionic surfactants in room-temperature ionic liquids including [BMIm] + [PF 6 ] − and [EMIm] + [Tf 2 N] − .…”

Self-association of cromolyn sodium in aqueous solution characterized by nuclear magnetic resonance spectroscopy

“…It has been shown that the observed chemical shift of a probe nucleus remains constant at concentrations below C CM for a non-ionic surfactant in water. 19 Compounds having rigid aromatic structures are believed to typically associate by nonmicellar processes involving face-to-face stacking of molecules. 20 In the present study, a spectral shift for the H6 proton was observed even at very low concentrations, although the changes were more pronounced at concentrations above 10 mg/ mL.…”

Origins of Pressure-Induced Protein Transitions

“…The latter can be scrutinized against the published data on the pressure dependences of the critical micelle concentrations of ionic and nonionic surfactants, including sodium alkylsulfates, alkyltrimethylammonium bromides, and n-alkyl polyoxyethylene ethers. [49][50][51][52][53][54][55] The critical micelle concentration of these surfactants exhibits an initial increase with pressure followed by a decrease with a maximum at around 1 kbar. This behavior is in satisfactory agreement with the pressure dependence of the free energy change we have calculated for the transfer of methylene groups from water to a micelle, which shows a maximum of ΔG at around 0.6 kbar.…”