Phenolic Hydroxyl‐Activated Lignin for Preparation of Extreme Environments Adaptive Adhesives

ABSTRACT Epoxy resins is widely applied in various industrial production. Lignin exhibits enormous potential as an alternate for health‐risk compound, bisphenol A, in the preparation of epoxy resin adhesives. However, the complicated structures and low reactivity limit the further utilization of lignin. In this study, a green deep eutectic solvent (DES) was utilized to enhance the phenolic hydroxyl content of hard wood organic lignin, from 3.63 to 5.63 mmol/g, to promote the reactivity of lignin during the preparation process of epoxy resin adhesives. Enabling by the DES induced lignin activation, the prepared lignin‐based epoxy resin exhibited excellent epoxy‐value (0.41 mol/100 g) and the as‐prepared adhesives possessed remarkable mechanical properties (tensile stress up to 50.86 MPa). Even after exposure to extreme conditions (freezing or soaking for 48 h), the adhesives maintained over 70% mechanical strength. This work contributes to the broader effort towards sustainable lignin‐based adhesives in industrial applications.