Preparation and characterization of tough and highly resilient nanocomposite hydrogels reinforced by surface‐grafted cellulose nanocrystals. Issue 40 (20th May 2021) - Li, Bengang
Abstract: Despite many strong and tough hydrogels have been fabricated according to the energy dissipating mechanism, they usually lack high resilience due to the presence of large hysteresis. Herein, poly ( N ‐vinylpyrrolidone) grafted cellulose nanocrystal (CNC‐g‐PVP) was used as special multifunctional physical crosslinkers to fabricate tough and highly resilient nanocomposite hydrogels. CNC‐g‐PVP with varying loading was incorporated into chemically crosslinked polyacrylamide (PAM) networks by in‐situ radical polymerization to give PAM/CNC‐g‐PVP nanocomposite hydrogels. Robust cooperative hydrogen bonds existed between the surface‐grafted PVP chains and the PAM matrix, which could rupture to dissipate energy upon deformation and recover instantly on the removal of stress. This unique energy dissipating mechanism led to excellent mechanical performance of the hydrogels. Their tensile elastic modulus, toughness, and compressive strength are 1.4–1.8, 2.1–3.0, and 1.44–2.73 times of pure PAM hydrogel, respectively. Moreover, the hydrogels exhibit low hysteresis, high resilience (ca. 97%) under cyclic tensile loading‐unloading and good recovery of hysteresis (ca. 90%) under cyclic compressive loading‐unloading. Abstract : The PAM/CNC‐g‐PVP nanocomposite hydrogels were hybrid crosslinked by covalent bonds and robust cooperative hydrogen bonds. The cooperative hydrogen bonds can rupture to dissipate energy upon deformation and recover instantly on the removal of stress in the elastic PAM matrix, leading to low hysteresis, high toughness, and resilience of the hydrogels.