Cellulose nanofibril-guided orienting response of supramolecular network enables superstretchable, robust, and antifatigue hydrogel

<p>Hydrogels featuring randomly networked matrix typically show poor mechanical strength owing to the weak interchain interactions of the matrix. Encouragingly, the stretchability and toughness of hydrogel materials along a certain direction were recently improved to an unprecedented level with the design of structured and oriented matrix, the realization of excellent and concurrently isotropic mechanical performance for hydrogels now become the next- research goal. Herein, a self-assembling process of poly(vinyl alcohol) (PVA) macromolecular chain and cellulose nanofibril (CNF) induced by the salting-out effect was reported, which allowed the formation of a strongly hydrogen-bonded PVA-CNF supramolecular matrix. The resulting hydrogel, in any direction, can show an ultra-high stretchability of 7,400% and a true tensile strength of 420 MPa through the orientation of the supramolecular matrix. The robustness of the supramolecular interaction between PVA and CNF was experimentally demonstrated by the fact that the hydrogel showed a high fracture energy (reaching up to 95.7 kJ m⁻²) and low notch sensitivity (fatigue threshold of 3,203 J m⁻²), even outperforming most state-of-the-art anisotropic hydrogels. These results highlight that constructing supramolecular interaction among various components of gel matrix holds great promise for the design of future gel materials with the extraordinary mechanical performance.</p>