Micellization of Carboxylic Acid Gemini Surfactant and Its Interaction with Amino Acid Surfactant in Aqueous Solution

The carboxylic acid-type Gemini surfactant (CGS12) was synthesized, and its micellization in aqueous solution at different pH values at 25.0 degrees C was investigated. The results show that the critical micelle concentration (CMC) of CGS12 at different pH values is only 10(-6) order of magnitude, and the pH has little effect on the CMC. Moreover, the interaction of CGS12 with amino acid surfactant of sodium N-lauroyl sarcosinate (SLS) at 25.0 degrees C and pH 7.0 was investigated using surface tension, dynamic light scattering (DLS), cryogenic transmission electron microscopy (Cryo-TEM), and Ross-Miles foam measurements. The CGS12/SLS mixture shows a low CMC, and as a whole the CMC value becomes smaller with increasing molar fraction of CGS12 (X-CGS12). Under different X-CGS12, the mixtures form soluble aggregates with different hydration radii (R-h). Moreover, the mixture aggregates are mainly in the form of vesicles. The foaming height of CGS12 is worse than that of SLS, but the CGS12/SLS mixture has good foaming stability. This work reveals that the surfactant mixture has good surface activity and good foam stability.