Molecular Self‐Aggregation of Tetradecylbenzene Sodium Sulfonate Isomers

Abstract

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.

NMR of liquid crystals and micellar solutions

“…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. 83 Cationic hydrocarbon surfactant, N-cetylpyridinium chloride (CPC), was mixed with an anionic fluorocarbon surfactant, 1,1,11-trihydroperfluorohendecylsulfate ammonium (THFHS). From CPC-richer side, with THFHS increasing, one observes the phase behavior sequence of L1-phase, L1/La-phase, single slightly turbid La-phase, then gel-like phase and finally a two-phase region with clear L1-phase at the top and ppts.…”