Cellulose nanocrystal nanocomposites capable of low-temperature and fast self-healing performance

The development of low-temperature self-healing polymers is crucial because high-temperature or softening conditions for rapid self-healing inevitably reduce their mechanical strength. Herein, we first report cellulose nanocrystal (CNC)/polymer nanocomposites with a rapid low-temperature self-healing performance. The nanocomposite was prepared by simple blending of grafted CNC and matrix prepolymer made from the monomers having metal-ligand coordination and lower critical solution temperature functionalities along with the presence of hexamethylene diisocyanate and dibutyltin dilaurate. Owing to the dynamic nature of both hydrogen bonds and metal-ligand coordinated covalent bonds, the resultant nanocomposites showed excellent self-healing efficiency (99 %, within 1 h) at a low temperature (5 °C) with robust mechanical properties including a high stretchability (230 %), high toughness (2538 MJ/m³), enhanced tensile strength (25.49 ± 0.02 MPa), and improved thermomechanical properties. Self-healing performance of the coordinated covalent bonds requiring active hydrogen was considerably improved by the introduction of CNCs with abundant hydrogen bonds.