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This paper deals with the effect of the surfactant isomeric structure on self-aggregation in aqueous solution. The relationship between the molecular structure of a series of tetradecylbenzene sulfonate isomers (with the benzene ring located at different positions along the alkyl chain) and surface tension was made clear. It is found that the critical micelle concentration increases and the surface tension at critical micellar concentration decreases as the benzene group moves toward the center of the alkyl chain. The structure of micelles was studied by 1 H-NMR relaxation, which indicates that the density of methylene protons in the surface layer of the micellar core decreases as the branching of the hydrophobic group increases. The spontaneous vesicle formation in aqueous solution was investigated by transmission electron microscopy. The results reveal that, as the benzene group moves toward the center of alkyl chain, the assembly structure changes from micelle to vesicle, then to lamellar bilayers, while the critical packing parameter increases.

A new method of synthesis a series of pure dialkylbenzene sulfonates is described. The benzene ring carries a major alkyl substituent, consisting of a linear chain of sixteen carbon atoms long, and one additional methyl group. Products are charactered by EI-MS and 1H NMR. Experimental investigations have been conducted to explore the interfacial tension behavior of crude oil with dialkylbenzenesulfonates. The effects of various parameters such as surfactant concentration, salinity concentration on the interfacial tension of crude oil-water were investigated in detail. The transient low interfacial tensions in crude oil/alkali system were caused by the synergistic effects between surfactant and the active species generated at interface, but surfactant molecules plays the dominant role at equilibrium.