Upgrading wood biorefinery: An integration strategy for sugar production and reactive lignin preparation

Lignin has been extensively explored as a renewable precursor for materials fabrication. However, its low reactivity is one of the main challenges for material development. Herein, we presented a simple and effective biorefinery strategy to directly prepare reactive lignin with lower molecular weight and enhanced reactivity for the fabrication of high-strength self-healing adhesives. The role of 2-naphthol to suppress lignin condensation during the organosolv pretreatment of two woody biomasses was demonstrated by the less condensed structures and decreased molecular weights of lignin. This promoted the enzymatic hydrolysis of pretreated poplar from 50.2% to 62.9% at the low enzyme loading. Furthermore, the resultant lignins showed 51.7% increase in the modification efficiency during an esterification reaction. Lignin based macro-initiator was used to initiate grafting from reversible addition-fragmentation chain transfer polymerization of furan methacrylate and lauryl methacrylate to generate copolymers with tunable properties. Then, the occurrence of reversible Diels-Alder reaction between furan rings and maleimide crosslinker enabled the formation of dynamic network as self-healing adhesive. The adhesiveness analysis revealed that the highest adhesive shear strength reached 6.3 MPa, which was significantly higher than most of previous adhesives used on wood chips. Furthermore, after 10 times self-healing, the shear strength still accomplished 39.6% of original strength. This study has presented an upgraded biorefinery strategy to tune the properties of lignin and its interesting utilization to fabricate functional materials, providing new insights into materials and biorefinery society.

Automated summary

This study presents a simple and effective biorefinery strategy to prepare reactive lignin with lower molecular weight and enhanced reactivity for the fabrication of high-strength self-healing adhesives. The role of 2-naphthol in suppressing lignin condensation during organosolv pretreatment was demonstrated, leading to increased enzymatic hydrolysis and modification efficiency. The resulting lignins were used to generate copolymers with tunable properties and self-healing adhesive properties through reversible Diels-Alder reactions. The adhesive shear strength reached 6.3 MPa, significantly higher than previous adhesives used on wood chips, and after 10 times self-healing, the shear strength still maintained 39.6% of the original strength.