The critical micelle concentration of tetraethylammonium perfluorooctylsulfonate in water

The aggregation characteristics of tetraethylammonium perfluorooctylsulfonate in water were studied by several techniques: conductivity, pH, ion-selective electrodes, and surface tension. It was concluded that the aggregation process is gradual and starts with the formation of oligomers such as ion pairs that grow to give spherical micelles, which become wormlike with increasing concentration. Because of the size and hydrophobicity of the counterion, micelles quickly increase in ionization degree up to about 0.5. Differences among different critical micelle concentration values in the literature are explained on the basis of the gradual formation of micelles.

Graphical abstractThis work reports the Krafft point of tetraethylammonium perfluorooctylsulfonate, and the dependence on temperature of the critical micelle concentration, the micellar ionization degree and Gibbs free energy, enthalpy and entropy of micellization, the apparent molar partial volume, thermal expansion coefficient, and the adiabatic compressibility factor of both micellized and unmicellized surfactant in water. Results are interpreted on the basis of dehydration of surfactant on micellization and on the temperature increase.Figure optionsDownload full-size imageDownload as PowerPoint slide