Hydrotropic salt promotes anionic surfactant self-assembly into vesicles and ultralong fibers.

Molecular self-assembly has become a versatile approach to create complex and functional nanoarchitectures. In this work, the self-assembly behavior of an anionic surfactant (sodium dodecylbenzene sulfonate, SDBS) and a hydrotropic salt (benzylamine hydrochloride, BzCl) in aqueous solution is investigated. Benzylamine hydrochloride is found to facilitate close packing of surfactants in the aggregates, inducing the structural transformation from SDBS micelles into unilamellar vesicles, and multilamellar vesicles. The multilamellar vesicles can transform into macroscale fibers, which are long enough to be visualized by the naked eye. Particularly, these fibers are robust enough to be conveniently separated from the surfactant solution. The combined effect of non-covalent interactions (e.g., hydrophobic effect, electrostatic attractions, and π-π interactions) is supposed to be responsible for the robustness of these self-assembled aggregates, in which π-π interactions provide the directional driving force for one-dimensional fiber formation.