Properties of quaternary ammonium surfactant with hydroxyethyl group and anionic surfactant mixed systems

Abstract The surface activities and application properties for the mixtures of cationic surfactant didecylmethylhydroxyethylammonium acetate (DEAQ) and anionic surfactant sodium fatty alcohol ether carboxylate (AEC 9 -Na) were studied systematically. The interaction parameters and thermodynamic micellization parameters of DEAQ/AEC 9 -Na mixtures were evaluated. Results showed that the mixed systems have higher surface activity, lower contact angle and better wetting ability than either component due to the synergistic effect and there are attractive interactions between molecules for the surfactant mixtures at the mixed micelles and the air/liquid interfaces. The thermodynamic parameters indicate that the micellization of the mixtures is an entropically driven process. When the mole fraction of DEAQ (α DEAQ ) is 0.608, the emulsifying capacity for liquid paraffin and soybean oil of DEAQ/AEC 9 -Na mixtures is the best among the mole ratios studied, and the emulsifying capacity of the mixtures is stronger than that of AEC 9 -Na except α DEAQ  = 0.509. For the mixed systems, the foaming ability is the best when α DEAQ  = 0.608, whereas the foam stability is the best when α DEAQ  = 0.280. And there were greater foaming abilities and foam stabilities for mixed systems than those of DEAQ.