Thermally healable and remendable lignin-based materials through Diels – Alder click polymerization

We report in this work the preparation and in-depth characterization of thermo-reversible healable materials based on lignin, a major naturally occurring aromatic biopolymer. Following an environmentally friendly chemical pathway, a derivative of soda lignin (SL) bearing maleimide groups and poly-functional furan linkers were clicked through the furan – maleimide Diels – Alder (D-A) polymerization in a solvent free media and without the use of catalyst. The furan linkers were obtained by the thiol – epoxy reaction between furfuryl glycidyl ether and thiols of functionalities from 2 to 4. The different degree of substitution of maleimide lignin derivatives and linker functionalities allowed the tuning of the thermo-mechanical properties of the resultant materials. The latter exhibit on demand thermally induced disassembly and reassembly of the polymeric networks when heated at 110–130 °C and then cured at 60 °C, providing controlled self-healing properties and an efficient reprocessing with a limited impact on the thermo-mechanical properties and the thermal stability of the final materials. This study provides interesting perspectives for the production of renewable lignin-based aromatic polymers, demonstrating that an effective chemical modification together with tailored molecular architectures could pave the way for the development of high value-added materials from this underused aromatic feedstock.