Abstract: The relationship of surface property and hydrophobic branched-chain structure was studied using four branched-alkylbenzenesulfonates with additional alkyl substituents synthesized by our laboratory. From the surface tension measurements in pure water and 0.171 mol·L－1 NaCl solutions, the following parameters were calculated: critical micelle concentration (cmc), the surface tension at the cmc (γcmc),surface excess at the cmc (Γmax),area per molecule at the cmc (Amin), pc20, and standard free energy of adsorption (DGadӨ).Lengthening the branched alkyl chain at the meta-position of sulfonic group,Γmax decreased while γcmc decreased; At the same time, cmc decreased, pc20 increased, and DGadӨ became more negative. These results indicated that the hard-disk areas of sodium branched-alkylbenzenesulfonate molecules (as) affected adsorption and surface tension.

Key words: Sodium branched-alkylbenzenesulfonates, 　Hard-disk areas of surfactant molecules, 　cmc, 　Saturation adsorption amount, 　Surface tension