Multiscale Self-Assembly of Mobile-Ligand Molecular Nanoparticles for Hierarchical Nanocomposites

Multiscale hierarchical morphologies are greatly desired for fabricating nanocomposites with tunable macroscopic properties, but challenges remain in precisely manipulating the spatial arrangement of nanoparticles in polymer matrices across multiple length scales. Here, we demonstrate a class of mobile-ligand nanoparticle system built upon 1 nm anionic polyoxometalate molecular nanoparticles and cationic terminated polymer chains by electrostatic interaction. The highly rearrangeable polymer chains can serve as mobile ligands to direct the polyoxometalates to align into sub-10 nm anisotropic superlattice-like nanoarrays in the bulk state. Moreover, these nanoarrays can further serve as structural units to assemble into hierarchically ordered morphologies in polymer matrices, e.g., percolated networks over hundreds of micrometers which are comprised of cylindrically packed polyoxometalate superlattices down to sub-10 nm scale. These hierarchical morphologies enable the nanocomposites with reinforced mechanical performance. The presented mobile-ligand approach can provide a paradigm to design functional polymer nanocomposites with improved properties such as mechanical reinforcement and collective optical and electronic functions

Hybrid Liquid-Crystalline Electrolytes with High-Temperature-Stable Channels for Anhydrous Proton Conduction

Modern electrochemical and electronic devices require advanced electrolytes. Liquid crystals have emerged as promising electrolyte candidates due to their good fluidity and long-range order. However, the mesophase of liquid crystals is variable upon heating, which limits their applications as high-temperature electrolytes, e.g., implementing anhydrous proton conduction above 100 °C. Here, we report a highly stable thermotropic liquid-crystalline electrolyte based on the electrostatic self-assembly of polyoxometalate (POM) clusters and zwitterionic polymer ligands. These electrolytes can form a well-ordered mesophase with sub-10 nm POM-based columnar domains, attributed to the dynamic rearrangement of polymer ligands on POM surfaces. Notably, POMs can serve as both electrostatic cross-linkers and high proton conductors, which enable the columnar domains to be high-temperature-stable channels for anhydrous proton conduction. These nanochannels can maintain constant columnar structures in a wide temperature range from 90 to 160 °C. This work demonstrates the unique role of POMs in developing high-performance liquid-crystalline electrolytes, which can provide a new route to design advanced ion transport systems for energy and electronic applications

Self-Assembled Construction of Ion-Selective Nanobarriers in Electrolyte Membranes for Redox Flow Batteries

Ion-conducting membranes (ICMs) with high selectivity are important components in redox flow batteries. However it is still a challenge to break the trade-off between ion conductivity and ion selectivity, which can be resolved by the regulation of their nanostructures. Here, polyoxometalate (POM)-hybridized block copolymers (BCPs) are used as self-assembled additives to construct proton-selective nanobarriers in the ICM matrix to improve the microscopic structures and macroscopic properties of ICMs. Benefiting from the co-assembly behavior of BCPs and POMs and their cooperative noncovalent interactions with the polymer matrix, ∼50 nm ellipsoidal functional nanoassemblies with hydrophobic vanadium-shielding cores and hydrophilic proton-conducting shells are constructed in the sulfonated poly­(ether ether ketone) matrix, which leads to an overall enhancement of proton conductivity, proton selectivity, and cell performance. These results present a self-assembly route to construct functional nanostructures for the modification of polymer electrolyte membranes toward emerging energy technologies