Abstract
Interaction between biosurfactant, [Glu1,Asp5]-iso-surfactin, and widely used synthetic surfactant, alkylbenzenesulfonate, will offer instructions for the applications of their binary systems. Physicochemical properties of mixed monolayers and mixed micelles, and their dependence on mixing ratios were explored by using of surface tension measurements, dynamic light scattering, and thermodynamic calculations. Results showed that synergism occurred when the mole ratio of surfactin to alkylbenzenesulfonate absorbed at air/water interface tends to be 1:1. Antagonism between surfactin and alkylbenzenesulfonate appeared when the air/water interface was covered nearly by one kind of surfactants. Surfactin constitutes predominant part both at air/water interface and in mixed micelles when its hydrophobicity is much higher than alkyl benzenesulfonate. Steric structure shows greater impact than the length of alkyl chain on the interaction between surfactin and alkylzbenzenesulfonate. With temperature increasing, the fraction of surfactin in the mixed monolayer decreased. While in mixed micelles, interaction between surfactin and alkyl benzenesulfonate didn’t show direct correlation with constitution of individual surfactant components, but largely with molecule structure, micelle size, and steric hindrance.
Graphical Abstract
Disclosure statement
The authors declare that they have no conflict of interest.