Extraordinary solution-processability of lignin in phenol-maleic anhydride and dielectric films with controllable properties

Highly efficient and cost-competitive dissolution of lignin is vital to value-added utilization of lignin waste streams. Here, a novel and cost-efficient supramolecular eutectic liquid (phenol-MAH) comprising phenol and maleic anhydride was developed, which can rapidly dissolve lignin with ultrahigh-solid loading (>50 wt%) at room temperature. About 70 wt% lignin loading in phenol-MAH leads to a highly cohesive plasticine state of lignin, which is unprecedented in lignin-based materials. Experimental and computational approaches revealed that the cooperation of strong pi-stacking and hydrogen-bonding interactions is responsible for the extraordinary solution-processability of lignin in phenol-MAH. Enhanced compatibility and activity of lignin are also ascribed to the phenolation and acylation of phenol-MAH. Furthermore, phenol-MAH was applied to develop renewable lignin-based dielectric films without solvent removal. The resulting films with a nano-network structure display highly tunable dielectric properties attributed to alpha-dispersion and the Maxwell-Wagner effect. The modulation of the crosslinking density leads to controllable mechanical properties (e.g. yield stress, 0.05-31.50 MPa) of the films by changing lignin loading. The tailored performance demonstrates that the bio-film can be used as a renewable dielectric material for transient electronics. The scalable phenol-MAH strategy is expected to facilitate the fabrication of novel functional bio-materials with high lignin-loading.