Low-temperature, ultra-fast, and recyclable self-healing nanocomposites reinforced with non-solvent silylated modified cellulose nanocrystals.

Developing polymeric materials with remarkable mechanical properties and fast self-healing performance even at low temperatures is challenging. Herein, the polymeric nanocomposites containing silane-treated cellulose nanocrystals (SCNC) with ultrafast self-healing and exceptional mechanical characteristics were developed even at low temperatures. First, CNC is modified with a cyclic silane coupling agent using an eco-friendly chemical vapor deposition method. The nanocomposite was then fabricated by blending SCNC with matrix prepolymer, prepared from monomers that possess lower critical solution temperature, followed by the inclusion of dibutyltin dilaurate and hexamethylene diisocyanate. The self-healing capability of the novel SCNC/polymer nanocomposites was enhanced remarkably by increasing the content of SCNC (0-3 wt%) and reaching (≥99 %) at temperatures (5 & 25 °C) within <20 min. Moreover, SCNC-3 showed a toughness of (2498 MJ/m3) and SCNC-5 displayed a robust tensile strength of (22.94 ± 0.4 MPa) whereas SCNC-0 exhibited a lower tensile strength (7.4 ± 03 MPa) and toughness of (958 MJ/m3). Additionally, the nanocomposites retain their original mechanical properties after healing at temperatures (5 & 25 °C) owing to the formation of hydrogen bonds via incorporation of the SCNC. These novel SCNC-based self-healable nanocomposites with tunable mechanical properties offer novel insight into preparing damage and temperature-responsive flexible and wearable devices.

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.