Properties of Mixed Systems of Sodium Dodecyl Diphenyl Ether Disulfonate and Cocamidopropyl Betaine

The surface activity and a series of application properties of the mixture of anionic surfactant sodium dodecyl diphenyl ether disulfonate (2A1) and amphoteric surfactant cocamidopropyl betaine (CAB) were studied by measuring surface tension, contact angle, foamability and foam stability, zeta potential, as well as the chelation efficiency of trisodium methylglycine diacetate (MGDA) to Cu 2+ . The interaction parameters and thermodynamic micellization parameters of the CAB/2A1 complex system were calculated. The results show that the CAB/2A1 complex system behaves good synergistic effect, such as giving higher surface activity, smaller contact angle, and better foaming performance than the individual surfactants. The CAB and 2A1 molecules show strong interactions in both mixed micelles and mixed monolayer at air-water interface, and thermodynamic parameters calculated confirm that the micellization process is entropy-driven. The mixture gives the smallest contact angle or the best wetting performance at X (CAB) = 0.9, and shows the best foamability and foam stability at X (CAB) = 0.78. In addition, the mixture can significantly enhance chelation of the MGDA to Cu 2+ .