2024-02-21 マサチューセッツ大学アマースト校
＜関連情報＞
- https://www.umass.edu/news/article/polymer-science-team-develops-additive-can-upcycle-wide-range-plastics
- https://onlinelibrary.wiley.com/doi/10.1002/anie.202316248
ラジカルリサイクル可能なビニル由来ポリマーのための多用途コモノマー添加剤 A Versatile Comonomer Additive for Radically Recyclable Vinyl-derived Polymers
Autumn M. Mineo, Prof. Reika Katsumata
Angewandte Chemie International Edition Published: 29 November 2023
DOI:https://doi.org/10.1002/anie.202316248
Graphical Abstract
Vinyl-derived polymers are notoriously challenging to recycle chemically. Herein, we report free-radical copolymerization of a cyclic allyl sulfide with several monomers, generating dynamic linkages for closed-loop cyclability. Scission via radical addition-fragmentation-transfer (AFT) dramatically reduces molar mass and preserves oligomer reactivity. Recycling by oligomer extension imparts tunable recovery molar mass and fosters upcycling.
Abstract
Radically-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.
