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The efficient strategy for lignin fractionation is of great significance for its valorization into aromatics, fine chemicals, and functional materials. In this work, inspired by the traditional gel filtration and pH-responding solubility of lignin, a pH-responsive lignin-based hydrogel was fabricated via a simple cross-linking reaction and used for specific fractionation of lignin. The fraction with a higher molecular weight, more flexible linkages, aliphatic hydroxyl and carboxyl groups, and a high S/G ratio tends to entangle or aggregate with the network of the hydrogel. The pore size and water absorbency of the hydrogel can be tuned in different pH environments. As the solution switches to an acid environment, the unabsorbed fraction was precipitated completely, while the absorbed fraction was held by the shrunken pores of the hydrogel and then released to the fresh alkaline solution. This new strategy will find a new green and smart pathway for the development of not only the pH-responsive hydrogel but also lignin valorization.

Vitrimers open new possibilities in the reprocess of epoxy and other thermosets. However, direct heating is not practical on many occasions, and the waste vitrimers would cause great harm to the environment. In this work, we propose to use kraft lignin (KL) to fabricate vitrimer with reprocessability and environmental friendliness. The lignin-based epoxy vitrimer was fabricated by blending epoxy-modi ed KL and poly(ethylene glycol) bis(carboxymethyl) ether (PEG-DCM). The obtained lignin-based epoxy vitrimer (EML/PEG-DCM) showed good light-to-heat capability. Under the infrared radiation (808 nm, 1 W cm -2 ) for only 30 s, the surface temperature of EML/PEG-DCM was over ∼148 °C, and reached the maximum at ∼231 °C for 5 min. This good light-to-heat effect can activate the dynamic 3D crosslinking networks and repair the vitrimer. The energy consumption of the light-controlled remolding process is only one-thousandth of the conventional hot-press. This study not only helps to explore the natural characteristics of lignins, promoting their functional and intelligent utilization but also provides a new raw material platform for the development of green vitrimer materials.

Vitrimers open new possibilities in the reprocess of epoxy and other thermosets. However, direct heating is not practical on many occasions, and the waste vitrimers would cause great harm to the environment. In this work, we propose to use kraft lignin (KL) to fabricate vitrimer with reprocessability and environmental friendliness. The lignin-based epoxy vitrimer was fabricated by blending epoxy-modified KL and poly(ethylene glycol) bis(carboxymethyl) ether (PEG-DCM). The obtained lignin-based epoxy vitrimer (EML/PEG-DCM) showed good light-to-heat capability. Under the infrared radiation (808 nm, 1 W cm-2) for only 30 s, the surface temperature of EML/PEG-DCM was over ∼148 °C, and reached the maximum at ∼231 °C for 5 min. This good light-to-heat effect can activate the dynamic 3D crosslinking networks and repair the vitrimer. The energy consumption of the light-controlled remolding process is only one-thousandth of the conventional hot-press. This study not only helps to explore the natural characteristics of lignins, promoting their functional and intelligent utilization but also provides a new raw material platform for the development of green vitrimer materials.

No abstract