This review presents insights into the fundamental challenges of wet adhesion, and the applications of catechol-functionalized hydrogels in diverse areas.
Polyelectrolyte complexation is critical to the formation and properties of many biological and polymeric materials, and is typically initiated by aqueous mixing1 followed by fluid–fluid phase separation, such as coacervation2–5. Yet little to nothing is known about how coacervates evolve into intricate solid microarchitectures. Inspired by the chemical features of the cement proteins of the sandcastle worm, here we report a versatile and strong wet-contact microporous adhesive resulting from polyelectrolyte complexation triggered by solvent exchange. After premixing a catechol-functionalized weak polyanion with a polycation in dimethyl sulphoxide (DMSO), the solution was applied underwater to various substrates whereupon electrostatic complexation, phase inversion, and rapid setting were simultaneously actuated by water–DMSO solvent exchange. Spatial and temporal coordination of complexation, inversion and setting fostered rapid (~25 s) and robust underwater contact adhesion (Wad ≥ 2 J m−2) of complexed catecholic polyelectrolytes to all tested surfaces including plastics, glasses, metals and biological materials.
Over the past decade, lithium‐ion batteries (LIBs) have been widely applied in consumer electronics and electric vehicles. Polymer electrolytes (PEs) play an essential role in LIBs and have attracted great interest for the development of next‐generation rechargeable batteries with high energy density. Due to the several practical applications of LIBs and high demands for LIBs performance, many state‐of‐the‐art PEs with different structures and functionalities have been developed to regulate the LIBs performance, especially their rate capability, cycling durability, and lifespan. In this review, the recent advances in high‐performance LIBs prepared using well‐defined PEs are summarized. The ion‐transport mechanisms and preparation techniques of various well‐defined PE classes compared to conventional PEs are also discussed. The aim is to elucidate the structure code for advanced PEs with optimized properties, including ionic conductivity, mechanical properties, processability, accessibility, etc. The existing challenges and future perspectives are also discussed, setting the basis for designing novel PEs for energy conversion applications.
Lithium extraction from salt lake brines is highly demanded to circumvent the lithium supply shortage. However, polymer nanofiltration membranes suffer from low lithium permeability while nanofluidic devices are hindered by complicated preparation and miniaturized scales despite high permeability. Here, the authors report a facile strategy to prepare positively charged nanofiltration membranes for ultrapermeable and selective separation of lithium ions from concentrated magnesium/lithium mixtures. A new electrolyte monomer (diaminoethimidazole bromide, DAIB) containing bidentate amine groups is designed to modify pristine polyamide composite membranes. Structure characterizations and simulations show that the DAIB modification brings about nano-heterogeneity that not only improves surface hydrophilicity, but also reduces water transport resistance through the ≈100 nm thick separation layer. Water permeance of the modified membrane improves fivefold and is coupled with good stability in 200-h continuous nanofiltration. It exhibits high lithium flux (0.7 mol m −2 h −1) for brines (Mg 2+ /Li + ratio 20) at 6 bar operation pressure.
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