Synergistic multiple hydrogen bonds and reversible crystallization effect enable ultra-tough, self-healing, and recyclable cellulose-enhanced elastomer

Incorporating dynamic covalent bonds into polyurethane (PU) elastomers contributes to exceptional self-healing and recyclable properties. However, further applications are seriously limited due to unsatisfying mechanical characteristics. Herein, a self-healing and ultra-robust nanocomposite elastomer is presented here that consists of polyurethane matrix and cellulose nanocrystals through the synergistic gradient hydrogen bonds and straininduced reversible crystallization effect. Multiple dynamic hydrogen bonds formed between cellulose nanocrystals (CNC) and polyurethane (PHHD) together with the strain-induced reversible crystallized physical network facilitate excellent mechanical properties while maintaining favorable self-healing ability. The introduction of cellulose nanocrystals significantly enhanced the binding energy of the nanocomposite polyurethane elastomer system, exhibiting an increase of 204.32 kJ/mol. Consequently, nanocomposite elastomers display a remarkable tensile strength (up to 50.1 MPa), ultra-high toughness (441.6 MJ/m3), and excellent fracture energy (214.5 kJ/m2) Furthermore, the result found that the introduction of cellulose nanocrystals can reduce the reaction activation energy and obtain nanocomposite elastomers with highly efficient self-healing (93.9 %). The innovative approach is expected to facilitate the development of high-strength, tough, and exceptional selfhealing elastomers in academia and industry.