Salt effect on the aggregation behaviors of an anionic carboxylate gemini and a cationic surfactant

The synthesis method and conditions for the carboxylate Gemini surfactant O,O'-bis(sodium 2-lauricate)-p-benzenediol (C(11)pPHCNa) were explored. Surface tension data of the single and mixed systems of catanionic (cationic with anionic) surfactants with different salt concentrations were used to determine the CMC values and to obtain the information of self-assembly behaviors of the surfactants. Aggregates' morphologies were observed by transmission electron microscopy (TEM) and speculation was made according to the viscosity measurement results. The results show that large spherical aggregates formed in the mixed solution, which tend to transfer into branched and wormlike mixed micelles with the increases of the salt concentration. The viscosity of the mixed solution was found to increase gradually corresponding to the change of the catanionic surfactant mixtures' morphology.