Bioinspired pullulan-tannic acid hydrogels with high toughness, stretchability, adhesion and self-healing properties

Inspired by the high-density hydrogen bonds in spider silk and the mussel adhesive mechanism, pullulan-tannic acid (TA) hydrogels with high stretchability, toughness, adhesiveness, and rapid self-healing capabilities were successfully fabricated via a hydrogen-bond-driven co-assembly strategy combined with controlled evaporation. Infrared spectroscopy confirmed the presence of hydrogen bonds between pullulan and TA, while scanning electron microscopy revealed the porous network structure of the hydrogels. The tensile strength (TS), Young's modulus (YM), and toughness values of PulTA5 hydrogels were 0.48 MPa, 19.17 MPa, and 268.10 MJ/m³, respectively, reflecting increases of 433.3 %, 1538.5 %, and 76.7 % compared to PulTA1 hydrogels. The self-healed PulTA5 hydrogels exhibited the highest TS and toughness, along with the lowest elongation at break (EAB) values among all tested hydrogels. Furthermore, PulTA5 hydrogels demonstrated the highest adhesion strength to glass, paperboard, and metal surfaces. These improvements are attributed to the formation of abundant hydrogen bonds and van der Waals forces in the PulTA5 system, as confirmed by molecular dynamics (MD) simulations, which enhance the cohesion of the hydrogel and contribute to its compact structure. This novel strategy for designing pullulan-based hydrogels that combine high toughness and self-healing properties holds promise for the development of biobased materials for food packaging applications.