A well-defined lignin-based filler for tuning the mechanical properties of polymethyl methacrylate

A green, low-cost, and high-performance filler is a key factor in the development of the polymer industry. Although lignin is an abundant and sustainable biopolymer in nature with great potential as a filler, its applications are commonly limited by its heterogeneity. Here, a series of well-defined lignin-based fillers (lignin-graft-polymethyl methacrylate, L-g-PMMA) were synthesized by using a universal approach of the combination of chemical modification with lignin fractionation. The structural analysis of lignin fractions and tensile tests reveal that the strength and toughness of the lignin-filled polymer blends (PMMA/L-g-PMMA) can be well tuned by the molecular weights, kinds and contents of S/G units and flexible/rigid linkages in lignin macromolecules. This study not only provides a simple and effective strategy to overcome the heterogeneity of lignin but also paves the way towards high-value utilization of lignin on a broader scale.