The crisis of plastic waste in the environment calls for new polymers that are designed specifically for recycling at the end of their life. Lignin, which is present in approximately 15–40% of woody biomass, is an attractive biobased source for polymers given its aromatic nature. However, the use of lignin in polymers is complicated by its own reactivity and heterogeneous structure, factors that also create difficulties for designing end-of-life solutions for lignin-based polymers. Here we demonstrate a chemical recycling technique that prevents the loss of functionality to lignin and produces a recycled precursor capable of entering back into the synthetic sequence for non-isocyanate polyurethane foams. This technique enables the depolymerization of the polymer and isolation of lignin with enhanced solubility and hydroxyl content so that it can be reused in second-generation polymers. Detailed structural analysis of lignin after chemical recycling reveals the insertion of ethylene glycol in the side-chain region during a high-pressure hydrolysis recycling procedure. The closed-loop recycling process for the lignin-derived non-isocyanate polyurethane foam demonstrates a pathway towards a circular economy.

环境中的塑料垃圾危机需要专门设计用于在其生命周期结束时回收的新型聚合物。木质素存在于大约 15-40% 的木质生物质中，鉴于其芳香性，它是一种有吸引力的聚合物生物基来源。然而，木质素在聚合物中的使用因其自身的反应性和异质结构而变得复杂，这些因素也为设计基于木质素的聚合物的报废解决方案带来了困难。在这里，我们展示了一种化学回收技术，该技术可防止木质素失去功能，并生产出能够重新进入非异氰酸酯聚氨酯泡沫合成序列的回收前体。该技术能够解聚聚合物并分离出溶解度和羟基含量更高的木质素，从而使其可以在第二代聚合物中重复使用。化学回收后木质素的详细结构分析表明，在高压水解回收过程中，乙二醇插入侧链区域。木质素衍生的非异氰酸酯聚氨酯泡沫的闭环回收过程展示了通往循环经济的途径。