浙江理工大学吕汪洋团队报道了通过升级回收废弃PET获得羧酸酐分子开关介导的可回收PECT。相关研究成果发表在2025年2月6日出版的《德国应用化学》。

聚对苯二甲酸乙二醇酯（PET）年产量超过7000万吨，主要用于一次性领域，造成了严重的环境污染。传统的化学回收，通常需要将聚合物解聚成单体，由于复杂的回收过程、过度使用不可回收的溶剂和低聚合物转化率而受到限制。

受蛋白质分子开关的启发，研究人员提出了一种基于缩聚原理的新型聚合物到聚合物回收策略，将废PET升级为含有分子开关的高价值可回收聚（乙烯-co-1,4-环己烷二甲醇对苯二甲酸酯）衍生物。当分子开关失活时，系统内会发生酸化反应，由于反应基团的不平衡，导致分子量快速可控地降低。相反，激活分子开关会触发闭环反应，使酸酐分离，从而产生等摩尔比的基团，从而促进分子量的增加。通过简单地将分子开关结合到基于熔融缩聚的缩合产物中，实现了闭环回收能力，而不需要过量的有机溶剂或复杂的解聚过程。

该研究不仅为最终用途的PET上循环提供了一条新途径，还为缩聚物的闭环可回收性引入了分子切换的创新概念，从而展示了大规模实施的巨大潜力。

附：英文原文

Title: Accessing a Carboxyl-Anhydride Molecular Switch-Mediated Recyclable PECT Through Upcycling End-of-Use PET

Author: Hongjie Zhang, Mingyuan Fang, Shihao Niu, Miaomiao Wang, Mingyu Gao, Qiuquan Cai, Gangqiang Wang, Wenxing Chen, Wangyang Lu

Issue&Volume: 2025-02-06

Abstract: Poly(ethylene terephthalate) (PET), with an annual production of exceeding 70 million tons, is mainly utilized in disposable fields and subsequently contribute to severe environmental pollution. Conventional chemical recycling, which typically involves depolymerizing polymer into monomers, is limited due to the intricate recycling process, excess using unrecyclable solvents and low polymer conversion. Inspired by protein’s molecular switches, we propose a novel polymer-to-polymer recycling strategy based on polycondensation principles upcycling waste PET to high-value recyclable poly(ethylene-co-1,4-cyclohexanedimethanol terephthalate) derivatives containing molecular switches. Upon deactivating the molecular switch, an acidification reaction occurs within the system, leading to a rapid and controllable reduction in molecular weight due to the imbalance of reactive group. Conversely, activating the molecular switch triggers a ring-closing reaction that detaches acid anhydrides, bringing about equal molar ratio of groups and thereby facilitating an increase in molecular weight. By simply incorporating a molecular switch into condensation products based on melt polycondensation, closed-loop recycling capability is achieved without necessitating excessive organic solvents or complex depolymerization processes. The present study not only presents a novel pathway for end-of-use PET upcycling but also introduces an innovative concept of molecular switching for the closed-loop recyclability of condensation polymers, thereby demonstrating significant potential for large-scale implementation.

DOI: 10.1002/anie.202420839

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202420839