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 similar to 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 QLCs. We leverage a readily synthesized, cost-effective zwitterionic monomer as the building block to construct normal lyotropic double gyroid (G(1)) mesophases that afford radical polymerization. Although self-assembly of the amphiphile in neat water forms no QLCs, additional phosphoric acid can drive the emergence of G(1) mesophases by inducing the non-constant interfacial curvature. An intriguing advantage exhibited by this polymerizable G(1) system is the ability to persist upon swelling by large volumes of commercially available cross-linkers, thereby effectively facilitating structural lock-in through photoinitiated cross-linking. High-brilliance synchrotron small-angle X-ray scattering has unambiguously confirmed the excellent retention of periodic G(1) morphologies in the mechanically robust polymers. Transmission electron microscopy further provides unprecedented, detailed visualization of the spacing and symmetry in the cross-linked G(1) 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.

Automated summary

A scalable strategy using photo-crosslinking of QLCs to fabricate polymeric membranes with interconnected nanopores is presented. The use of a readily synthesized zwitterionic monomer to construct G(1) mesophases enables structural lock-in. High-brilliance synchrotron small-angle X-ray scattering and transmission electron microscopy confirm the structural preservation and detailed visualization of the materials.