The usual understanding in polymer electrolyte design is that increasing the polymer dielectric constant results in reduced ion aggregation and therefore increased ionic conductivity. We demonstrate here that in a class of polymers with extensive metal-ligand coordination and tunable dielectric properties, the extent of ionic aggregation is delinked from the ionic conductivity. The polymer systems considered here comprise ether, butadiene, and siloxane backbones with grafted imidazole side-chains, with dissolved Li + , Cu 2+ , or Zn 2+ salts. The nature of ion aggregation is probed using a combination of X-ray scattering, electron paramagnetic resonance (in the case where the metal cation is Cu 2+ ), and polymer field theorybased simulations. Polymers with less polar backbones (butadiene, and siloxane) show stronger ion aggregation in X-ray scattering compared to those with the more polar ether backbone. The Tg-normalized ionic conductivities were however unaffected by extent of aggregation. The results are explained on the basis of simulations which indicate that polymer backbone polarizability does impact the microstructure and the extent of ion aggregation, but does not impact percolation, leading to similar ionic conductivity regardless of the extent of ion aggregation. The results emphasize the ability to design for low polymer Tg through backbone modulation, separately from controlling ion-polymer interaction dynamics through ligand choice.

Polymer electrolytes with high Li + -ion conductivity provide a route toward improved safety and performance of Li + -ion batteries. However, most polymer electrolytes suffer from low ionic conduction and an even lower Li + -ion contribution to the conductivity (the transport number, t + ), with the anion typically transporting over 80% of the charge. Here, we show that subtle and potentially undetected associations within a polymer electrolyte can entrain both the anion and the cation. When removed, the conductivity performance of the electrolyte can be improved by almost 2 orders of magnitude. Importantly, while some of this improvement can be attributed to a decreased glass transition temperature, T g , the removal of the amide functional group reduces interactions between the polymer and the Li + cations, doubling the Li + t + to 0.43, as measured using pulsed-field-gradient NMR. This work highlights the importance of strategic synthetic design and emphasizes the dual role of T g and ion binding for the development of polymer electrolytes with increased total ionic conductivity and the Li + ion contribution to it.

Polymer-derived ceramics (PDCs) have enabled the development of nonoxide ceramic coatings and fibers with exceptional thermo-mechanical stability. Here, we report the self-assembly based synthesis of gyroidal (space group Q 230 , Ia3̅ d) mesoporous silicon oxynitride ceramic monoliths by pyrolysis of blends of commercially available preceramic polysilazane with a structure-directing triblock terpolymer up to temperatures of 1000 °C. Monoliths had pore diameters of 9.4 ± 1.1 nm and surface area of 160 m 2 /g. The threedimensionally (3D) ordered periodic pore structure of the as-made hybrids acts to relieve stresses by allowing the escape of gases formed during ceramization. This process in turn enables the retention of smooth monoliths during ceramization under ammonia, a process that both adds nitrogen to the material and removes carbon pyrolysis products. The monoliths are appealing for high-temperature applications such as catalyst supports and microelectromechanical system (MEMS) devices including gas and pressure sensors, as well as strong, stiff, and creep-resistant scaffolds for ordered interpenetrating phase composites.

Properties arising from ordered periodic mesostructures are often obscured by small, randomly oriented domains and grain boundaries. Bulk macroscopic single crystals with mesoscale periodicity are needed to establish fundamental structure-property correlations for materials ordered at this length scale (10-100 nm). We report on a solvent evaporation-induced crystallization method providing access to large (mm to cm sized) single crystal mesostructures in thick films (>100 µm), specifically bicontinuous gyroids, derived from block copolymers. After in-depth crystallographic characterization of single-crystal block copolymer-preceramic nanocomposite films, the structures are converted into mesoporous ceramic monoliths, with retention of mesoscale crystallinity. When fractured, these monoliths display single crystal-like cleavage along mesoscale facets. The method