Promoting Negative Gaussian Curvature in Lyotropic Liquid Crystal Systems with Oleate-Derived Gemini Surfactants

Abstract

Lyotropic liquid crystals (LLCs) are formed by solvent-driven microphase separation of amphiphilic molecules to yield assemblies with hydrophilic and hydrophobic domains. Commonly observed mesophases include: lamellae (flat curvature), cylinders, sphere packings, and network phases. Unlike lamellae and cylinders, which have constant mean curvature, networks phases deviate from constant mean curvature with local regions of flat curvature and negative Gaussian curvature (NGC) or “saddle-splay”. Lyotropic liquid crystals (LLCs) are excellent platforms for studying the formation of NGC interfaces because they are well-controlled systems with many tunable parameters. This thesis focuses on molecular amphiphilic designs that promote network LLC phase formation by trying to create packing mismatch between the hydrophilic and hydrophobic regions though the use of long-tail gemini dicarboxylates with unsaturated tails. Small angle X-ray scattering was used to observe the phase behavior of potassium oleate and tetramethylammonioum oleate, as well as preliminary exploration of the oleate-derived gemini surfactant.