Abstract: The relationships between the structures of sodium alkylbenzensulfonates with additional side chains and surface properties, especially the influence of the side chains, were studied. From the surface tension measured in pure water and 0.171 mol·L-1 NaCl solutions, the following parameters were calculated：the critical micelle concentration (cmc), the surface excess concentration at surface saturation (Гmax), the minimum area (Amin), the surface tension at the cmc (γmax), the effectiveness of a surfactant in reducing surface tension (πcmc), the efficiency of a surfactant in reducing surface tension(pC20), the standard free energy change upon adsorption (ΔGad0). The main chain and side chain have different effects on the surface properties. With increasing the number of carbons in the main chain or the side chains, cmc decreases, but the decrease degree of cmc is quite different, the main chain decreases cmc to a greater degree than the side chains do. While the number of carbons increases, the main chain increases Гmax, but the side chain decreases Гmax. These surface properties were explained by the structures of sodium alkylbonzensulfonate with additional side chains.

Key words: Alkylbenzensulfonate, Molecular structure, Critical micelle concentration, Surface excess concentration