Strategies for lignin depolymerization and reconstruction towards functional polymers

The depletion of petroleum resources and the growth of environmental problems have led to the need for alternative polymer materials with renewability and degradability. Lignin is a promising natural carbon source for the construction of polymer materials to replace petroleum resources, with the advantages of renewability, large reserves, wide distribution, bio-degradability, aromatic moieties, and low cost. Biorefining or the depolymerization of lignin is considered essential for lignin valorization and solving the intrinsic issues of lignin in functional polymer preparation. The aromatic monomers obtained from lignin depolymerization and the functional polymers constructed from the monomers are the current research focus for lignin utilization. In this review, we discuss the common depolymerization strategies ( i.e. chemical and biological depolymerization), classify aromatic monomers obtained from depolymerization ( i.e. vanillin, syringaldehyde, eugenol, ferulic acid, and sinapic acid derived monomers and p -coumaryl, coniferyl, and syringyl alcohols derived monomers), and systematically present various functional polymers constructed from these monomers. This review focuses on lignin depolymerization strategies and functional polymer construction based on lignin-derived monomers.