Large crystalline domains homogenization <i>via</i> solvent exchange-coupled dry annealing for ultrastrong and ultratough hydrogels

<p>Current hydrogel fabrication techniques often fall short of simultaneously optimizing key structural parameters, such as network uniformity, crosslinking density, and crystalline domain size, essential for achieving superior mechanical performance. Herein, we introduce a solvent exchange coupled dry-annealing technique, revolutionizing the synthesis of polyvinyl alcohol (PVA) hydrogels. This strategy seamlessly integrates the uniformity afforded by solvent exchange with the benefits of anisotropic densification and crystallization induced by dry annealing, thereby transforming the microstructural configuration of polymer networks, achieving unprecedented uniformity, along with adjustable crystalline domains density and size. Consequently, the resulting PVA hydrogels feature a robust, highly organized network with densely packed, and large crystalline domains. These hydrogels exhibit extraordinary mechanical strength with stress levels reaching 34.15 MPa and toughness (up to 95.21 MJ m^-3) , supplemented by a fracture energy of 99.2 kJ m^-2, significantly outperforming traditional hydrogels. Further enhancement of mechanical properties was achieved through a salting-out process, boosting strength to 52.5 MPa and toughness to 167.9 MJ m^-3. This advancement not only ushers in a new era of hydrogel technology but also opens avenues for creating advanced hydrogels with tailored mechanical properties for a variety of sophisticated applications.</p>