Regulating Lignin-Based Epoxy Vitrimer Performance by Fine-Tuning the Lignin Structure

Lignin is the second most abundant lignocellulosic biomass, and as a natural polymer, it shows great potential in preparing functional materials to meet the demand for green/sustainable development. Unfortunately, the inherent heterogeneity of lignin largely limits its applications. Furthermore, the effect of the lignin structure on the performance of the final materials has seldom been investigated. In this work, a totally biobased dynamic cross-linked vitrimer with up to 70% lignin content was successfully prepared from epoxidized fractionated lignin and sebacic acid without additional chemical modifications. The lignin structure effect on the performance of the resultant lignin-based epoxy vitrimers (LEVs) was systematically investigated. The experimental results show that the phenolic hydroxyl content and the ratio of flexible to rigid linkages in lignin have strong correlations with the tensile strength, toughness, self-repair ability, and reprocessability of the resultant LEVs. Meanwhile, the molecular weight and the S/G ratio of lignin show strong correlations with the thermal properties of the resultant materials. This study not only presents a fundamental study regarding the relationships between lignin properties, and the resultant LEVs have great potential applications as advanced packaging materials for light-sensitive commodities due to the inherent UV resistance of lignin.