Lignin is a highly abundant renewable natural resource with a unique structure, abundant reserves, and low cost. However, largescale utilization based on lignin still remains challenging due to its heterogeneity and inhomogeneity. Herein, we report the fabrication of tunable and mechanically tough lignin-based thermosetting epoxy resins with outstanding thermal stability by optimizing epoxidation conditions and the crosslinker. The obtained lignin-based bisphenol A composites show a tensile strength of 11.5 MPa, Young's modulus of 5.0 MPa, and heat resistance index temperature (T s ) up to 160.0 °C by tailoring the dosage of epichlorohydrin. It was found that the introduction of oxirane moieties on the lignin backbone limitedly improved the interfacial compatibility of the composite. Moreover, the enhanced mechanical and thermal properties were ascribed to the incorporation of modified lignin segments into the epoxy networks and the corresponding alternation of crosslink structures. Overall, this work provides a viable pathway to produce cost-efficient biobased materials with controlled mechanical properties for adhesives and engineering plastics.

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The structure of cellulolytic enzyme lignin (CEL) prepared from three bamboo species (Neosinocalamus affinis, Bambusa lapidea, and Dendrocalamus brandisii) has been characterized by different analytical methods. The chemical composition analysis revealed a higher lignin content, up to 32.6% of B. lapidea as compared to that of N. affinis (20.7%) and D. brandisii (23.8%). The results indicated that bamboo lignin was a p-hydroxyphenyl-guaiacyl-syringyl (H-G-S) lignin associated with p-coumarates and ferulates. Advanced NMR analyses displayed that the isolated CELs were extensively acylated at the γ-carbon of the lignin side chain (with either acetate and/or p-coumarate groups). Moreover, a predominance of S over G lignin moieties was found in CELs of N. affinis and B. lapidea, with the lowest S/G ratio observed in D. brandisii lignin. Catalytic hydrogenolysis of lignin demonstrated that 4-propyl-substituted syringol/guaiacol and propanol guaiacol/syringol derived from β-O-4′ moieties, and methyl coumarate/ferulate derived from hydroxycinnamic units were identified as the six major monomeric products. We anticipate that the insights of this work could shed light on the sufficient understanding of lignin, which could open a new avenue to facilitate the efficient utilization of bamboo.