Mussel-Inspired Tough Double Network Hydrogel As Transparent Adhesive

Hydrogels with excellent adhesive and mechanical properties have attracted extensive attraction, whereas few tough and sticky hydrogels have been successfully prepared with desirable and tunable performance. In this work, dopamine-modified hyaluronic acid (HA-DM) was first introduced to the double network (DN) system, which greatly improved the adhesive and mechanical performance of the original HA-acrylamide (AAm) DN hydrogel. The prepared mussel-inspired hydrogel features instant and flexible bonding capability (adhesive strength up to 90 kPa) and high transparency (transmittance up to nearly 100%), which could serve as a novel type of transparent adhesive for various uses. Moreover, by modulating external parameters such as pH, Fe3+ and HA-DM concentration of the precursor solution, protonation state of hyaluronic acid and chemical cross-linking density of PAAm chains within the hydrogel network could be controlled to achieve well-tuned mechanical and adhesive properties. Meanwhile, the structure-property relationship of this hydrogel system was further investigated by establishing correlation between overall hydrogel properties and internal structural parameters obtained by rheology, swelling ratio, and scanning electron microscopy (SEM) tests. Therefore, as an effective approach to enhancing the adhesive and mechanical properties of the hydrogel, this mussel-inspired practice would provide valuable insight into designing a functional hydrogel and elastomer for various applications.