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.

Stabilizing a Double Gyroid Network Phase with 2 nm Feature Size by Blending of Lamellar and Cylindrical Forming Block Oligomers

“…There is also strong interest in miniaturization of the self-assembled NET feature sizes down to sub-2 nm for applications such as nanofiltration and nanopatterning. 24 − 27 In diblock polymer systems, microphase segregation in the mean-field limit requires the product of the chain length ( N ) and Flory–Huggins interaction parameter (χ) to be greater than 10.5 (for the LAM morphology), and successful efforts have been made to prepare “high χ–low N ” materials with reduced domain sizes. 28 − 37 For example, NET phases with sub-5 nm domain spacing are observed in glycolipids and T-shaped liquid crystals.…”

Highly Ordered Interconnected 1 nm Pores in Polymers Fabricated from Easily Accessible Gyroid Liquid Crystals

“…The nontrivial challenge is manifested in the formulation of polymerizable Q LLCs by amphiphilic monomers to afford radical polymerization. Although non-reactive Q LLCs can be stabilized by tailored amphiphilic molecules with a high degree of structural flexibility, such as Gemini surfactants and synthetic lipids (e.g., monoolein), − attachment of common polymerizable moieties onto amphiphilic architectures, in general, reduces the tendency of Q LLC generation. For instance, due to the synthetic modularity, acrylate (AC) and methacrylate (MA) groups have been frequently incorporated into the construction of amphiphilic monomers .…”

A Lyotropic Liquid Crystal from a Flexible Oligopeptide Amphiphile in Dimethyl Sulfoxide

“…Obviously, these polymer-based LCs usually involve complex structures and challenging synthesis. To circumvent these issues, low-molecular-weight compounds have rapidly emerged, which self-assemble into an ordered LC phase in certain solvents. − Among others, oligopeptide-based LCs are very appealing. First, oligopeptides can be produced easily in a large scale through the solid-phase peptide synthesis (SPPS).…”