Nanoporous Polymer Networks Templated by Gemini Surfactant Lyotropic Liquid Crystals

Abstract

Nanoporous polymers with periodic, ordered structures have attracted significant interest for their potential applications as drug delivery vehicles, biomaterials, separations membranes, and materials for energy storage. Inducing polymer nanostructure through lyotropic liquid crystal-templated (LLC-templated) cross-linking photopolymerizations offers a promising means for morphological control at smaller length scales, which are difficult to access by other established strategies. We report the synthesis of a gemini dicarboxylate surfactant that self-assembles in water to form various aqueous LLC mesophases over a broad range of amphiphile concentrations, with an especially strong propensity to form the coveted bicontinuous double gyroid (GI) network mesophase. Aqueous GI LLCs surprisingly persist upon incorporation of as much as 10-37 wt % hexane-1,6-diol dimethacrylate (HDDMA) into the hydrophobic domains of these supramolecular surfactant assemblies, and cross-linking photopolymerization of the HDDMA unexpectedly proceeds with retention of this intricate LLC nanostructure. The nanoporous nature of the resulting templated polymers remains after surfactant removal by solvent extraction, as manifested by increased swelling ratios in water and 2-propanol as compared to isotropic materials of similar compositions. The exquisite level of control over polymer network porosity provided by templating within GI phases furnishes a promising new route toward nanostructured hydrophobic polymers.