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 strain-induced 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 self-healing elastomers in academia and industry.