Functions of Cationic Surfactant - Solubilization

Solubilization

Solubilization refers to the effect of the surfactant on increasing the solubility of poorly soluble or insoluble materials in water. For example, the solubility of benzene in water is 0.09% (volume fraction). If a surfactant (such as sodium oleate) is added, the solubility of benzene can be increased to 10%.

Solubilization is inseparable from the micelles formed by the surfactant in water. The micelles are micelles formed by the hydrocarbon chains in the surfactant molecules that are brought together in an aqueous solution due to hydrophobic interaction. The inside of the micelle is actually a liquid hydrocarbon, so non-polar organic solutes that are insoluble in water such as benzene and mineral oil are more soluble in the micelle. Solubilization is a process in which micelles dissolve the lipophilic substances and is a special effect of the surfactant. Therefore, only when the concentration of the surfactant in the solution is above the critical micelle concentration, there are more large micelles in the solution. Solubilization is only present, and the larger the micelle volume, the greater the amount of solubilization.

Different from solubilization and emulsification, emulsification is a discontinuous, unstable multiphase system obtained by dispersing a liquid phase into water (or another liquid phase). On the contrast, the solubilization results in a single-phase homogeneous stable system in which the solubilizing solution is in the same phase as the solubilized material. Sometimes the same surfactant has both emulsification and solubilization, but it only has a solubilization when its concentration is above the critical micelle concentration.