New polymers, properly designed for end-of-life and efficiently formed from renewable carbon, are key to the transition to a more sustainable circular plastics economy. Ring-opening polymerization (ROP) of bicyclic lactones is a promising method for the production of intrinsically recyclable polyesters, but most lactone monomers lack an efficient synthesis route from biobased starting materials, even though this is essential to sustainably account for material loss during the life cycle. Herein, we present the exceptionally rapid and controlled polymerization of a fully biobased tricyclic oxanorbornene-fused γ-butyrolactone monomer (M1). Polyester P(M1) was formed in low dispersity (D̵ = 1.2–1.3) and controllable molecular weight up to M_n = 76.8 kg mol^–1 and exhibits a high glass transition temperature (T_g = 120 °C). The orthogonal olefin and lactone functionalities offer access to a wide range of promising materials, as showcased by postpolymerization modification by hydrogenation of the olefin, which increased polymer thermal stability by over 100 °C. Next to rapid hydrolytic degradation and solvolysis, the poly(oxanorbornene-fused γ-butyrolactone) could be cleanly chemically recycled back to the monomer (CRM), in line with its favorable ceiling temperature (T_c) of 73 °C. The density functional theory (DFT)-computed ΔH° of ring-opening with methanol of γ-butyrolactone-based monomers provided a model to predict T_c, and the DFT-computed and X-ray crystal structure-derived structural parameters of M1, hydrogenated analogue M1-H₂, and regioisomer M2 offered insights into the structural descriptors that cause the high polymerizability of M1, which is key to establishing structure–property relations.

中文翻译：

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生物基聚（氧降烯熔融 γ-丁内酯）的闭环化学回收


新型聚合物经过适当设计，可回收碳有效形成，是向更可持续的循环塑料经济过渡的关键。双环内酯的开环聚合 （ROP） 是生产本质可回收聚酯的一种很有前途的方法，但大多数内酯单体缺乏从生物基起始材料的有效合成途径，尽管这对于可持续地解决生命周期中的材料损失至关重要。在此，我们提出了全生物基三环氧降冰烯熔融 γ-丁内酯单体 （M1） 的异常快速和受控聚合。聚酯 P（M1） 以低分散性 （D̵ = 1.2–1.3） 和可控分子量形成，最高可达 M_n = 76.8 kg mol^–1，并表现出较高的玻璃化转变温度 （T_g = 120 °C）。正交烯烃和内酯官能团为各种有前途的材料提供了使用权，烯烃加氢后的聚合改性证明了这一点，它将聚合物热稳定性提高了 100 °C 以上。 除了快速水解降解和溶剂分解外，聚（氧冰片烯熔融γ-丁内酯）可以通过化学方式清洁地回收回单体 （CRM），符合其 73 °C 的有利最高温度 （T_c）。 基于 γ-丁内酯的单体用甲醇开环的密度泛函理论 （DFT） 计算的 ΔH° 为预测 T_c 提供了一个模型，而 M1、氢化类似物 M1-H₂ 和区域异构体 M2 的 DFT 计算和 X 射线晶体结构衍生的结构参数为导致 M1 高聚合性的结构描述符提供了见解，这是建立结构-属性关系的关键。