Novel Gel Phase Formed by Mixing a Cationic Surfactive Ionic Liquid C16mimCl and an Anionic Surfactant SDS in Aqueous Solution

The phase behavior of a catanionic system composed by a cationic surfactive ionic liquid (IL), 1-hexadecyl-3-methylimidazolium chloride ([C(16)mim]Cl), an anionic sodium dodecyl sulfate (SDS), and water has been investigated. A novel gel phase with quite high water content can be fabricated showing similar theological properties to vesicles usually formed in traditional catanionic systems. The lamellar structure could also be constructed in SDS-rich region. Both the hydrophobic interaction of alkyl chains and interactions between oppositely charged head groups play important roles for the gel formation. Such a facile method to form gels directly from the catanionic system at relative low surfactant concentrations is novel, which should be related to the specific molecular structure of imidazolium ILs. The obtained results are expected to be helpful for better understanding of catanionic systems.