Stabilizing Differential Interfacial Curvatures by Mismatched Molecular Geometries: Toward Polymers with Percolating 1 nm Channels of Gyroid Minimal Surfaces

Abstract

Soft materials with self-assembled networks possess saddle-shaped interfaces with distributed negative Gaussian curvatures. The ability to stabilize such a geometry is critically important for various applications but can be challenging due to the possibly "deficient" packing of the building blocks. This nontrivial challenge has been manifested, for example, by the limited availability of crosslinkable bicontinuous cubic (Q) liquid crystals (LCs), which can be utilized to fabricate compelling polymers with networked nanochannels uniformly sized at ∼1 nm. Here, we devise a facile approach to stabilizing cross-linkable Q mesophases by leveraging the synergistic self-assembly from pairs of scalably synthesized polymerizable amphiphiles. Hybridization of the molecular geometries by mixing significantly increases the propensity of the local deviations in the interfacial curvature specifically required for Q assemblies. "Normal" (type 1) double gyroid LCs possessing 1 nm ionic channels conforming to minimal surfaces can be formulated by simultaneous hydration of the amphiphile mixtures, as opposed to the formation of hexagonal or lamellar mesophases exhibited by the single-amphiphile systems, respectively. Fixation of the bicontinuous network in polymers via radical polymerization has been efficaciously facilitated by the presence of the bifunctional polymerizable groups in one of the employed amphiphiles. High-fidelity lock-in of the ordered continuous 1 nm channels has been unambiguously confirmed by the observation of single-crystal-like diffraction patterns from synchrotron small-angle X-ray scattering and large-area periodicities by transmission electron microscopy. The produced polymeric materials exhibit the required mechanical integrity as well as chemical robustness in a variety of organic solvents that benefit their practical applications for selective transport of ions and molecules.

Highly Ordered Gyroid Nanostructured Polymers: Facile Fabrication by Polymerizable Pluronic Surfactants

“…SAXS characterizations of the UV-cross-linked polymers with varying R consistently indicated the characteristic diffraction peaks of the group 230 symmetry, revealing the retained integrity of GYR assemblies, regardless of the EDDET fraction (Figure c). This structural resilience contrasts with the previous findings in the polymerizable small-molecule LCs that require a high level of cross-linking to kinetically trap the assemblies. − …”

“…Alternatively, polymerization of small-molecule liquid crystals (LCs) provides a pathway to achieving sub-5 nm feature sizes. ,− However, the pursuit of ordered GYR morphologies through polymerizable LCs requires a precise molecular design and the time-consuming synthesis of LC monomers. The need to integrate polymerizable groups into the mesogenic blocks introduces additional lateral polarity and steric hindrance, often obstructing the formation of the desired assemblies. , Furthermore, their polymerization risks structural disruption due to the alteration of the packing geometries from monomers to polymers, ,, thereby compromising the predictability of the resulting nanostructures.…”

“…The need to integrate polymerizable groups into the mesogenic blocks introduces additional lateral polarity and steric hindrance, often obstructing the formation of the desired assemblies. , Furthermore, their polymerization risks structural disruption due to the alteration of the packing geometries from monomers to polymers, ,, thereby compromising the predictability of the resulting nanostructures. Only a select few GYR LCs are viable for creating polymers that can retain networked morphologies. ,− While the issue of structural disruption can be overcome through extensive cross-linking, the consequent brittleness of the resulting polymers significantly compromises the mechanical adaptability. − , …”

“…Subsequent UV-induced polymerization solidifies the original gel-like mesophases (Figure b) with high nanostructured fidelity, independent of the cross-linking degree (Figure c). This characteristic stands in contrast with small-molecule LC, which necessitate rapid and dense cross-linking to preserve their ordered structures, − , thereby enabling tunable mechanical properties.…”

Gyroid Liquid Crystals as Quasi-Solid-State Electrolytes Toward Ultrastable Zinc Batteries

“…Triply periodic minimal surface (TPMS) structures, characterized by mesmerizingly intricate geometric patterns and infinite three-dimensional (3D) surfaces, have garnered substantial interest in various scientific disciplines. − TPMS structures, celebrated for their inherent mathematical elegance, embody a delicate balance of the curvature and symmetry. Beyond their natural efficiency and geometric grace, their potential for optimizing ion transport has drawn attention .…”