Linker Length-Dependent Control of Gemini Surfactant Aqueous Lyotropic Gyroid Phase Stability

Abstract

Network-phase lyotropic liquid crystals (LLCs) derived from the water-directed self-assembly of small molecule amphiphiles comprise a useful class of soft nanomaterials, with wide-ranging applications in structural biology and membrane science. However, few known surfactants enable access to these mesophases over wide temperature and amphiphile concentration phase windows. Recent studies have demonstrated that gemini ("twin tail") dicarboxylate surfactants, in which alkyl carboxylates are covalently linked near the headgroups by a hydrophobic bridge, exhibit increased propensities to form double gyroid network phase LLCs. We demonstrate herein that the lyotropic self-assembly behaviors of gemini dicarboxylates sensitively depend on the linker length, whereby odd-carbon linkers stabilize the double gyroid network LLC over unprecedented amphiphile concentration windows up to ∼45 wt % wide between T ≈ 22-80 °C. These self-assembly phenomena, which arise from the linker length-dependent preferred molecular conformations of these amphiphiles, will broaden the technological applications of these nanostructured LLCs.

Keywords: amphiphiles; double gyroid; lyotropic liquid crystals; nanostructured materials; self-assembly; surfactants.