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

Polymerization of bicontinuous cubic (Q) liquid crystals (LCs) can be utilized to produce technologically useful polymeric materials with 3-D interconnected nanopores of ∼1 nm. However, their practical applications have been hindered by the exceptionally complicated syntheses of the needed polymerizable amphiphiles and the susceptible morphological destruction upon polymerization. Here, we present a scalable strategy to fabricate polymeric membranes with 3-D interconnected nanopores by photo-crosslinking of easily accessible Q LCs. We leverage a readily synthesized, cost-effective zwitterionic monomer as the building block to construct "normal" lyotropic double gyroid (G1) mesophases that afford radical polymerization. Although self-assembly of the amphiphile in neat water forms no Q LCs, additional phosphoric acid can drive the emergence of G1 mesophases by inducing the non-constant interfacial curvature. An intriguing advantage exhibited by this polymerizable G1 system is the ability to persist upon swelling by large volumes of commercially available cross-linkers, thereby effectively facilitating structural lock-in through photo-initiated cross-linking. High-brilliance synchrotron small-angle X-ray scattering has unambiguously confirmed the excellent retention of periodic G1 morphologies in the mechanically robust polymers. Transmission electron microscopy further provides unprecedented, detailed visualization of the spacing and symmetry in the cross-linked G1 assemblies over large areas. The exceptionally easy access to the building blocks and the high-fidelity structural preservation enable the scalable fabrication of nanoporous membranes for applications such as ionic transportation, as preliminarily demonstrated.