Mechanically robust eutectogels enabled by precisely engineered crystalline domains
Résumé
Eutectogels have emerged as promising candidates for technological applications due to their environmental stability, repeatable deformability, and high ionic conductivity. Nevertheless, the existing eutectogels often show fragile network structures, in which the simultaneous achievement of high modulus, strength, and toughness remains a real challenge. Herein, a variabletemperature solvent exchange (VTSE) strategy is proposed to fabricate mechanically robust eutectogels. The VTSE approach implements a two-stage solvent exchange process to synergistically optimize the crystal nucleation and growth of poly(vinyl alcohol), resulting in a robust network crosslinked by well-developed crystalline domains. The obtained eutectogels exhibit an advantageous combination of high Young's modulus (103.1 MPa), strength (40.5 MPa), toughness (86.8 MJ m -3 ), and fracture energy (98.7 kJ m -2 ), surpassing the performance of conventional hydrogels, organogels, and ionogels. Moreover, the versatility of VTSE approach allows its application to other solvent systems, providing a powerful platform for the design of advanced functional gels.
High-performance gels with good mechanical properties and environmental stability are in great demand for a wide range of applications. In biomedical engineering, load-bearing tissue scaffolds require gels with high modulus and strength to mimic the mechanical performance of natural tissues 1-4 . In energy storage devices, gel electrolytes with adequate toughness and environmental stability are essential for ensuring safety and durability of flexible supercapacitors and batteries 5-8 . Furthermore, the development of stretchable and wearable electronics necessitates mechanically robust gels that possess favorable fatigue resistance to withstand repeated deformations 9-11 . Nonetheless, conventional gels, such as hydrogels, organogels, and ionogels, often fail to meet these stringent requirements due to their inherent shortcomings, including inadequate mechanical strength, poor environmental stability, high cost, and toxicity 12-14 . Eutectogels, defined as polymer networks swollen with liquid deep eutectic solvent (DES) as the continuous phase, have recently emerged as a promising class of gels to address these limitations 15-17 . DES is a mixture of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) featuring negligible volatility, high thermal stability, wide electrochemical window, and good conductivity 18,19 . These properties endow eutectogels with versatility, making them attractive candidates for various applications. Moreover, the facile preparation of DES by mixing two or more components offers a cost-effective and eco-friendly platform for fabricating advanced functional gels 20 . Nevertheless, simultaneously achieving high modulus, strength, and toughness in eutectogels remains a huge challenge, stemming from conflicting structural requirements. High modulus and strength typically demand densely crosslinked networks with restricted chain mobility, whereas high toughness necessitates energy dissipation mechanisms (e.g., sacrificial bonds or chain sliding) that often compromise stiffness 21,22 .
In the pursuit of high-performance gels, researchers have explored various tactics, such as inducing abundant polymer chain entanglements 22,23 , constructing dynamic crosslinked networks 24,25 , elaborating bio-inspired multi-scale tough composites 26,27 , and
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