Water-Wire Networks: New Avenue for Engineering Polymer Membranes Using Bioinspired Artificial Water Channels

Artificial water channels (AWCs) are supramolecular mimics of biological water channel protein aquaporins (AQPs). AWCs research is focused on providing selective water permeation pathways across biomimetic membranes through one-dimensional water-wires seen in AQPs. This characteristic molecular transport behavior has spurred the introduction of AWC into polymeric matrices in order to overcome current polymer membranes’ molecular separation limits. However, thus far, AWCs could not compete with the evolutionally optimized AQPs in terms of water and solute transport property, and it has hampered development of AWC-based membranes. Here, we propose a new strategy for engineering AWCs in order to achieve AQP-like water permeability with enhanced water-to-salt permselectivity that exceeds current desalination membranes’ trade-off by four orders of magnitudes. It was achieved by introducing a new type of AWC, peptide-appended hybrid[4]arenes (PAH[4]) that self-clusters in the membranes. The dynamic scaffolds of PAH[4] clusters enabled water molecules to be aligned in and around each channel structures, and to be highly interconnected, and resulted in formation of water-wire networks. These networks maintain characteristic feature of water-wires seen in AQPs that have restricted interactions with channel scaffolds by avoiding hydrogen-bonding with channel walls, but provide synergistically increased number of permeation pathways. Therefore, the structural and functional properties of PAH[4]s, which are more stable and processable than protein water channels, are expected to be a strong candidate for design of new bioinspired polymeric membranes for water and energy related molecular separations.