The primary challenge in solid-state polymer electrolyte membranes (PEMs) is to enhance properties, such as modulus, toughness, and high temperature stability, without sacrificing ionic conductivity. We report a remarkably facile one-pot synthetic strategy based on polymerization-induced phase separation (PIPS) to generate nanostructured PEMs that exhibit an unprecedented combination of high modulus and ionic conductivity. Simple heating of a poly(ethylene oxide) macromolecular chain transfer agent dissolved in a mixture of ionic liquid, styrene and divinylbenzene, leads to a bicontinuous PEM comprising interpenetrating nanodomains of highly cross-linked polystyrene and poly(ethylene oxide)/ionic liquid. Ionic conductivities higher than the 1 mS/cm benchmark were achieved in samples with an elastic modulus approaching 1 GPa at room temperature. Crucially, these samples are robust solids above 100 °C, where the conductivity is significantly higher. This strategy holds tremendous potential to advance lithium-ion battery technology by enabling the use of lithium metal anodes or to serve as membranes in high-temperature fuel cells.

Self-assembly of ABA triblocks in ionic liquids provides a versatile route to highly functional physical ion gels, with promise in applications ranging from plastic electronics to gas separation. However, the reversibility of network formation, so favorable for processing, restricts the ultimate mechanical strength of the material. Here, we describe a novel ABA system that can be chemically cross-linked in a second annealing step, thereby providing greatly enhanced toughness. The ABA triblock is a poly(styrene-b-ethylene oxide-b-styrene) polymer in which about 25 mol % of the styrene units have a pendant azide functionality. After self-assembly of 10 wt % triblock in the ionic liquid [EMI][TFSA], the styrene domains are cross-linked by annealing at elevated temperature for ca. 20 min. The high ionic conductivity (ca. 10 mS/cm) of the physical ion gels is preserved in the final product, while the tensile strength is increased by a factor of 5.

Polymer electrolytes are alternatives to liquid electrolytes traditionally used in electrochemical devices such as lithium-ion batteries and fuel cells. In particular, block polymer electrolytes are promising candidates because they self-assemble into well-defined microstructures, in which orthogonal properties can be integrated into a single material (e.g., high modulus in domain A, fast ion transport in domain B). However, the performance of block polymer electrolytes often falls short, due to the lack of long-range continuity of both domains and relatively low strength. We recently reported a simple, one-pot synthetic strategy to prepare polymer electrolytes with the highest reported combination of modulus and ionic conductivity, attributes enabled by a co-continuous, cross-linked network morphology. In this work we aim to understand the mechanism by which this nanoscale morphology is formed by performing a series of in situ, time-resolved experimentssmall-angle X-ray scattering, conductivity, rheology, and reaction kineticsto monitor the electrolyte as it transitions from a macroscopically homogeneous liquid to a microphase-separated solid. The results suggest that the chain connectivity of the diblock gives rise to isotropic concentration fluctuations that increase in amplitude and coherence such that the network morphology is ultimately produced. The kinetic trapping of this network morphology by chemical cross-linking prior to the ordering transition is shown to be critically important to the resulting advantageous bulk electrolyte properties.

A new nanoscale sensing concept for the detection of nitroaromatic explosives is described. The design consists of nitroaromatic‐selective polymeric layers deposited inside microfabricated trenches. As the layers are exposed to nitroaromatic vapors, they swell and contact each other to close an electrical circuit. The nitroaromatic selective polymer, poly(4‐vinylpyridine) (P4VP), is deposited in the trenches using initiated chemical vapor deposition (iCVD). P4VP is characterized for the first time as a selective layer for the absorption of nitroaromatic vapors. The Flory–Huggins equation is used to model the swelling response to nitroaromatic vapors. The Flory–Huggins interaction parameter for the P4VP–nitrobenzene system at 40 °C is 0.71 and 0.25 for P4VP–4‐nitrotoluene at 60 °C. Sensing of nitrobenzene vapors is demonstrated in a prototype device, while techniques to improve the performance of the design in terms of response time and sensitivities are described. Modeling shows that concentration and mass limits of detection of 0.95 ppb and 3 fg, respectively, can be achieved.