Abstract: Foaming properties and dynamic surface tension(DST) of aqueous solutions of a series of sodium 2,4,5-trialkyl benzene sulfonates and sodium 2,5-dialkyl benzene sulfonates were determined. The parameters of DST (t*, n, R_1/2) were correlated with the foaming ability of the same surfactant solution. The results indicate that the molecular diffusion in the solution, adsorption and arrangement on the air/water interface were changed with the changes of molecular structures: with the increase of the alkyl chain length, the values of t* and n increase, and the value of R_1/2 decreases. For 2,4,5-trialkyl benzene sulfonates, 2-alkyl and 5-alkyl have strong steric hindrance, which have a strong influence on the molecular arrangement on the air/water interface, with increasing the chain length, foam stability decreases. While the 4-alkyl chain has a weak influence on the structure of adsorption film, the 4-alkyl chain almost doesn't influence the foam stability. For 2,5-dialkyl benzene sulfonates, the branched-alkyl chain is more flexible, which is characterized by more densely packed adsorbed molecules and higher film elasticity of the adsorption film. Therefore, the foam stability is higher than that of sodium 2,4,5-trialkyl benzene sulfonates. In the case of modified Bikerman method, DST is the key factor controlling the foaming ability.

Key words: Sodium alkylbenzenesulfonate, Molecular structure, Dynamic Surface Tension, Foaming properties