Supramolecular interactions enable pseudo-nanophase separation for constructing an ion-transport highway

A well-defined hydrophilic/hydrophobic nanophase-separated structure is widely applied for the construction of fast ion-transport pathways in polymeric membranes for energy-related applications such as electrochemical reactors, fuel cells, and redox flow batteries (RFBs). Conventional nanophase separation is induced by covalently grafted side chains, which however complicate membrane preparation and potentially reduce the chemical stability of membranes. In this work, we report a pseudo-nanophase-separation strategy enabled by supramolecular interactions to construct fast and selective ion-transport channels in polymeric membranes. The "side chains" are "grafted" onto the polymer backbone via supramolecular interactions instead of covalent bonds, simplifying the membrane preparation process and simultaneously protecting the polymer backbone from chemical degradation, which is a critical problem usually found in membranes with molecular modifications. The pseudo-nanophase separation enables high-performance membranes for aqueous acidic RFBs, showing high efficiency and good cycling stability, which suggests its potential to design highly conductive and chemically stable membranes for various energy-related devices.