Dodecagonal quasicrystals of oil-swollen ionic surfactant micelles

A delicate balance of noncovalent interactions directs the hierarchical self-assembly of molecular amphiphiles into spherical micelles that pack into three-dimensional periodic arrays, which mimic intermetallic crystals. Herein, we report the discovery that adding water to a mixture of an ionic surfactant and n-decane induces aperiodic ordering of oil-swollen spherical micelles into previously unrecognized, aqueous lyotropic dodecagonal quasicrystals (DDQCs), which exhibit local 12-fold rotational symmetry and no long-range translational order. The emergence of these DDQCs at the nexus of dynamically arrested micellar glasses and a periodic Frank-Kasper (FK) sigma phase approximant sensitively depends on the mixing order of molecular constituents in the assembly process and on sample thermal history. Addition of n-decane to mixtures of surfactant and water instead leads only to periodic FK A15 and sigma approximants with no evidence for aperiodic order, while extended ambient temperature annealing of the DDQC also reveals its transformation into a sigma phase. Thus, these lyotropic DDQCs are long-lived metastable morphologies, which nucleate and grow from a stochastic distribution of micelle sizes formed by abrupt segregation of varied amounts of oil into surfactant micelles on hydration. These findings indicate that molecular building block complexity is not a prerequisite for the formation of aperiodic supramolecular order, while also establishing the generic nature of quasicrystalline states across metal alloys and self-assembled micellar materials.

Automated summary

The addition of water to a mixture of an ionic surfactant and n-decane was found to induce the formation of aqueous lyotropic dodecagonal quasicrystals, which exhibit local 12-fold rotational symmetry and no long-range translational order. The formation of these quasicrystals is sensitive to the mixing order of molecular constituents and sample thermal history, with different conditions leading to the formation of only periodic structures. These findings suggest that molecular complexity is not always required for the formation of aperiodic supramolecular order.