Enthalpies of micellization of the quaternary tetradecyl- and -cetyl ammonium salts

Thermodynamics of Cationic Surfactant Sorption onto Natural Clinoptilolite

“…The enthalpy data from the micelle system did not reflect an additional contribution from demicellization as HDTMA sorbed below the ECEC. The enthalpy of micellization, about Ϫ9.7 kJ/mol (31)(32)(33), is close to the measured enthalpies of sorption. This suggests that the dominant enthalpic effect is the transfer of HDTMA from the water phase to the bound phase, regardless of the HDTMA structure on the surface or in solution.…”

“…For the 15 CH 2 -CH 2 bonds in the HDTMA molecule, the predicted transfer energy is then between 25.5 and 42 kJ/mol. A total value for micellization of HDTMA also can be calculated or measured to be about Ϫ32 kJ/mol (18,(31)(32)(33). The ⌬G spec values for sorption above the ECEC (obtained using TEA as a measure of ⌬G elec ) are Ϫ18.3 and Ϫ25.5 kJ/mol, respectively, for the monomeric and micellar HDTMA systems.…”

Effect of Temperature on Micelle Formation in Aqueous NaBr Solutions of Octyltrimethylammonium Bromide

“…There have been only few publications (10,(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33) on the effect of added salt on the micelle formation in aqueous salt solutions of alkyltrimethylammonium bromides.…”

Effect of Electrolyte (NaCl) and Temperature on the Mechanism of Cetyl Trimethylammonium Bromide Micelles

“…The CMC data obtained for CTAB in the presence of electrolyte at different temperature are given in Table 3, which show that addition of electrolyte with different concentration decreases the CMC value of surfactant. Electrolyte decreases CMC; because the ions of the salts neutralized the charge on the micelle surface thus deceasing the thickness of ionic compound around the surfactant and electrostatic repulsion between them helping in this way to micellization process (Paredes et al 1984). Electrolyte like NaCl lowered the CMC of surfactants that can be explained by the fact that Na + and Cl -ions in solution can affectively screen the attractive electrostatic attraction between charged headgroups with surfactant leading to aggregation at lower surfactant concentration which results in increase in hydrophobicity, and decrease in the CMC. In the presence of ionic liquid, value of CMC is lowered due to increasing concentration of counter ions or due to the formation of mix micelle.…”