Self-Assembled Vesicles Formed by Positional Isomers of Sodium Dodecyl Benzene Sulfonate-Based Pseudogemini Surfactants.

ABSTRACT

The construction of pseudogemini surfactants based on noncovalent interactions (such as electrostatic interaction and π-π stacking) was a powerful method to assemble well-defined aggregates in aqueous solution. The mixtures of butane-1,4-bis(methylimidazolium bromide) ([mim-C4-mim]Br2) and positional isomers of sodium dodecyl benzene sulfonate (SDBS-0,11 or SDBS-3,8) in a molar ratio of 12 were studied to characterize the effect of straight and branched alkyl chains on the aggregation behavior of pseudogemini surfactants. Spontaneous phase transition from micelles to vesicles was formed by these two kinds of complexes. Interestingly, a densely stacked onion-like structure (multilamellar vesicles) with more than one dozen layers was fabricated. The micelle and vesicle phases were characterized in detail by cryogenic transmission electron microscopy, polarized optical microscopy, dynamic light scattering, and rheological measurements. It can be clearly demonstrated that the structure of alkyl chain can significantly influence the surface adsorption, solution self-assembly, and aqueous two-phase system of pseudogemini surfactants. Our work provided a convenient technique to achieve controlled self-assembly by introducing positional isomers of surfactants.