Role of Poly(ethylene glycol) Di(meth)acrylate Cross-linkers in Modulating Structures of Hexagonal Lyotropic Liquid Crystal toward Enhanced Nanofiltration

Hexagonal lyotropic liquid crystals (HLLCs) have become a very attractive nanostructured template for fabricating nanofiltration active layers. While introducing cross-linkers into HLLC stabilizes their structure via covalent networks, it often compromises interfacial stability. We investigated this trade-off using solid-state NMR and small-angle X-ray scattering. We found that a poly(ethylene glycol) di(meth)acrylate (PEGDA) cross-linker with a medium chain length (nine units) and a bulky end group optimally stabilizes the HLLC interface. The medium chain ensures targeted localization within hydrophilic domains, while the bulky group provides steric hindrance, minimizing disruptive interactions with surfactants. This structural synergy enables significantly higher cross-linker loading without inducing phase transitions. Consequently, the heavily cross-linked system maintains well-ordered hexagonal mesophases with continuous, defect-free water pathways. This structural integrity translates to a dramatic enhancement in the permeability of the HLLC-templated active layer, increasing from 1.6 to 7 L m –2 h –1 bar –1 μm.