AbstractRadically‐formed, vinyl‐derived polymers account for over 30 % of polymer production. Connected through stable carbon‐carbon bonds, these materials are notoriously challenging to chemically recycle. Herein, we report universal copolymerization of a cyclic allyl sulfide (CAS) additive with multiple monomers under free‐radical conditions, to introduce main‐chain dynamic motifs. Backbone allyl sulfides undergo post‐polymerization radical rearrangement via addition‐fragmentation‐transfer (AFT) that fosters both chain scission and extension. Scission is selectively induced through allyl sulfide exchange with small molecule thiyl radicals, resulting in oligomers as low as 14 % of the initial molar mass. Crucially, oligomers retain allyl sulfide end groups, enabling their extension with monomer under radical conditions. Extended, i.e., recycled, product molar mass is tunable through the ratio of monomer to oligomer, and can surpass that of the initial copolymer. Two scission‐extension cycles are demonstrated in copolymers with methyl methacrylate and styrene without escalation in dispersity. In illustration of forming higher‐value products, i.e., upcycling, we synthesized block copolymers through the extension of oligomers with a different vinyl monomer. Collectively, our approach to chemical recycling is unparalleled in its ability to 1) function in a variety of vinyl‐derived polymers, 2) complete radical closed‐loop cycling, and 3) upcycle waste material.
摘要 由乙烯基衍生的聚合物占聚合物产量的 30% 以上。这些材料通过稳定的碳-碳键连接在一起,在化学回收方面具有很大的挑战性。在此,我们报告了一种环状烯丙基硫醚(CAS)添加剂与多种单体在自由基条件下的通用共聚,以引入主链动态图案。骨架烯丙基硫醚通过加成-断裂-转移(AFT)发生聚合后自由基重排,从而促进链的断裂和延伸。通过烯丙基硫醚与小分子硫自由基的交换,可选择性地诱导断裂,从而产生低至初始摩尔质量 14% 的低聚物。最重要的是,低聚物保留了烯丙基硫醚末端基团,使其能够在自由基条件下与单体延伸。延伸(即回收)后的产品摩尔质量可通过单体与低聚物的比例进行调整,并可超过初始共聚物的摩尔质量。在甲基丙烯酸甲酯和苯乙烯共聚物中演示了两个裂解-扩展循环,分散性没有增加。为说明如何形成更高价值的产品(即升级循环),我们用不同的乙烯基单体延伸低聚物,合成了嵌段共聚物。总之,我们的化学循环方法在以下方面具有无与伦比的能力:1)可用于各种乙烯基聚合物;2)完成激进的闭环循环;3)对废料进行升级循环。