Developing sustainable polymers with low-value lignin remains a challenge. Herein, lignin-containing repairable polyimines were synthesized with tailored properties using lignin fractionation. First, softwood Kraft lignin is fractionated into a more homogeneous fraction with a lower molecular weight and a higher OH content. Next, Kraft lignin and its fraction are esterified by levulinic acid to introduce active ketone groups and subsequently condensed with oleylamine (OAm) and bis(3-aminopropyl)-terminated polydimethylsiloxane (PDMS) via a catalyst-free Schiff-base reaction to form grafted lignin-OAm copolymers and cross-linked lignin-PDMS polymer networks (MKL-P and MFL-P), respectively. Results show that lignin-OAm polyimines can be self-repaired and hot reprocessed under pressure, while lignin-PDMS polyimines can be repaired with the assistance of a healing agent, heat, and pressure. Dynamic mechanical analyses demonstrate that the stress–relaxation behaviors of the polyimines follow the Arrhenius law under thermal-stress activation, indicating the occurrence of transimination. Moreover, compared with Kraft lignin, the lignin fraction ameliorates the grafting density of ketones and enhances the cross-linking density of lignin-PDMS polyimine networks. The higher cross-linking density of MFL-P leads to superior stress–relaxation activation energy, thermal stability, hydrophobicity, and light-shielding ability but inferior repairability and translucency. This work provides insights into the polymerization of lignin-based polymer networks and the potential application of lignin-PDMS polyimines for repairable, translucent, anti-UV, and hydrophobic coatings.

中文翻译：

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通过木质素分馏合成具有定制性能的生物基可修复聚亚胺

使用低价值木质素开发可持续聚合物仍然是一个挑战。在此，使用木质素分馏合成了具有定制特性的含木质素的可修复聚亚胺。首先，软木硫酸盐木质素被分馏成更均匀的部分，具有较低的分子量和较高的羟基含量。接下来，硫酸盐木质素及其馏分被乙酰丙酸酯化，引入活性酮基团，随后与油胺（OAm）和双（3-氨丙基）封端的聚二甲基硅氧烷（PDMS）通过无催化剂席夫碱反应缩合形成接枝物分别是木质素-OAm 共聚物和交联木质素-PDMS 聚合物网络（MKL-P 和 MFL-P）。结果表明，木质素-OAm 聚亚胺可以在压力下进行自修复和热再加工，而木质素-PDMS 聚亚胺可以在修复剂、热和压力的帮助下进行修复。动态力学分析表明，在热应力激活下，聚亚胺的应力松弛行为遵循阿伦尼乌斯定律，表明发生了转胺化。此外，与硫酸盐木质素相比，木质素部分改善了酮的接枝密度并提高了木质素-PDMS聚亚胺网络的交联密度。 MFL-P 较高的交联密度导致优异的应力松弛活化能、热稳定性、疏水性和遮光能力，但可修复性和半透明性较差。这项工作深入了解了木质素基聚合物网络的聚合以及木质素-PDMS 聚亚胺在可修复、半透明、抗紫外线和疏水涂层中的潜在应用。