Bio-based composite hydrogel/film reinforced by hyperbranched lignin nanoparticles: Robustness, thermostability, thermal insulation and UV shielding

Most of the bio-based hydrogels tend to malfunction under a high-temperature condition, as the crosslinked network structure readily disintegrates, failing to meet the demands of hot environment. Herein, we exploit a thermostable composite hydrogel (CH) mainly using bio-based hyperbranched lignin nanoparticles (H-LNPs), TEMPO-oxidized cellulose nanofibers (TOCN), and scleroglucan (Slg), followed by a slow evaporation to form a multifunctional CH film. Thanks to the uniform distribution of H-LNPs and TOCN, which are rich in hydroxyl groups, within the hydrogel matrix, the crosslinking density, storage modulus, loss modulus, and thermal stability of the CHs are remarkably enhanced. As a result, the optimum CH demonstrates excellent thermal resistance and structural stability even after 196 h at 140 °C. Moreover, the resultant CH film exhibits outstanding UV shielding (>99.8 %) and solar radiation shielding (cooling 6.6 °C), endowing it as an ideal candidate for thermal insulation. These findings underscore the potential of H-LNPs in the development of robust, thermostable, and thermally insulating hydrogels for industrial applications in extreme environments.