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.