Inverse Pm3n cubic micellar lyotropic phases from zwitterionic triazolium gemini surfactants

Abstract

Inverse lyotropic liquid crystal phases comprising spatially-limited aqueous nanodomains have potentially wide-ranging applications, including the encapsulation and selective delivery of small molecules and as aqueous nanoreactors for molecular catalysis. We report the aqueous self-assembly of two homologous, zwitterionic bis(alkyltriazolium sulfobetaine) gemini surfactants into previously unknown inverse cubic micellar phases with Pmn symmetry (space group #223). Using temperature-dependent X-ray scattering, we demonstrate that these highly ordered, inverse discontinuous micellar phases are stable over remarkably wide amphiphile concentration windows between T = 30–90 °C at ambient pressure. These observations suggest that the packing arrangements adopted by structurally anisotropic gemini surfactants enable ready access to only the third known inverse micellar lyotropic phase, and the first one to exhibit a tetrahedral close-packing of inverse micelles.