Unusually Stable Aqueous Lyotropic Gyroid Phases from Gemini Dicarboxylate Surfactants

Abstract

Aqueous lyotropic liquid crystal (LLC) assemblies with bicontinuous cubic morphologies (Q-phases) have shown promise in applications ranging from selective chemical separations to ion transporting media, yet universal design criteria for amphiphiles that adopt these unique structures remain elusive. Recent reports have demonstrated that cationic gemini surfactants exhibit a tendency to form bicontinuous cubic LLCs as compared to single-tail amphiphiles; however, the universality of this surfactant design motif in stabilizing Q-phases remains untested. Herein, we report the modular synthesis of a new class of anionic gemini surfactants derived from aliphatic carboxylic acids and demonstrate their unexpectedly strong propensity to form gyroid LLC phases with unprecedented stability between 25 and 100 °C over amphiphile concentration windows up to 20 wt % wide. By systematically varying the alkyl spacer length and surfactant counterions (Na⁺, K⁺, and (CH₃)₄N⁺), we identify molecular motifs that favor formation of technologically useful bicontinuous cubic LLC morphologies.