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The development of mild methods to depolymerize polymers has become increasingly important in our current Age of Plastics, and ball‐mill grinding (BMG) is emerging as a promising candidate. In this report, we demonstrate that subjecting poly(α‐methyl styrene) (PMS) to BMG leads to high extents of depolymerization (up to 64 mol% of α‐methyl styrene was produced) with minimal side products after only minutes of grinding. Constrained geometries simulate external force (CoGEF) simulations and radical trapping experiments supported that the depolymerization was initiated by mechanochemical chain scission. Depolymerization proceeded despite bulk temperatures remaining far below that of the ceiling temperature of PMS. Control experiments suggested that the extent of depolymerization was equilibrium controlled. Polystyrene and poly(methyl methacrylate) also underwent depolymerization, although to a much lesser degree (up to 4% monomer produced), presumably due to their much higher ceiling temperatures. This work provides an entry point for further development of BMG as a tool for the depolymerization of vinyl polymers under mild conditions. [ABSTRACT FROM AUTHOR]

Enyne monomers derived from D‐xylose underwent living cascade polymerizations to prepare new polymers with a ring‐opened sugar and degradable linkage incorporated into every repeat unit of the backbone. Polymerizations were well‐controlled and had living character, which enabled the preparation of high molecular weight polymers with narrow molecular weight dispersity values and a block copolymer. By tuning the type of acid‐sensitive linkage (hemi‐aminal ether, acetal, or ether functional groups), we could change the degradation profile of the polymer and the identity of the resulting degradation products. For instance, the large difference in degradation rates between hemi‐aminal ether and ether‐based polymers enabled the sequential degradation of a block copolymer. Furthermore, we exploited the generation of furan‐based degradation products, from an acetal‐based polymer, to achieve the release of covalently bound reporter molecules upon degradation. [ABSTRACT FROM AUTHOR]

Self-immolative polymers (SIPs) are unique macromoleculesthatare able to react to multiple types of environmental influences bygiving amplified response outputs. When triggering moieties installedat SIP chain ends are activated by their corresponding stimuli, aspontaneous head-to-tail depolymerization ensues, often involvingmultitopic release of small molecules. SIP designs have evolved ahigh degree of modularity in each of their functional components,enablinga broad range of utility and applications-driven tuning. In this Perspective,we summarize and discuss recent progress in this nascent area of research,including (i) synthesis of different types of SIPs, (ii) design andevaluation of triggering moieties, (iii) depolymerization mechanismsand kinetics, (iv) applications of SIPs, and (v) outlook and challengesfacing the field. [ABSTRACT FROM AUTHOR]

Titelbild: Sugar-Based Polymers from d-Xylose: Living Cascade Polymerization, Tunable Degradation, and Small Molecule Release (Angew. Keywords: cascade reactions; degradation; metathesis; polymerization; sugars EN cascade reactions degradation metathesis polymerization sugars 521 521 1 01/06/21 20210111 NES 210111 B D-Xylose b kann in ein polymerisierbares Monomer auf der Basis von Enin-Zucker umgewandelt werden, wie auf dem Titelbild zu sehen ist. Cascade reactions, degradation, metathesis, polymerization, sugars. [Extracted from the article]

We explored the mechanochemical degradation of bottlebrush and dendronized polymers in solution (with ultrasonication, US) and solid states (with ball-mill grinding, BMG). Over 50 polymers were prepared with varying backbone length and arm architecture, composition, and size. With US, we found that bottlebrush and dendronized polymers exhibited consistent backbone scission behavior, which was related to their elongated conformations in solution. Considerably different behavior was observed with BMG, as arm architecture and composition had a significant impact on backbone scission rates. Arm scission was also observed for bottlebrush polymers in both solution and solid states, but only in the solid state for dendronized polymers. Motivated by these results, multi-mechanophore polymers with bottlebrush and dendronized polymer architectures were prepared and their reactivity was compared. Although dendronized polymers showed slower arm-scission, the selectivity for mechanophore activation was much higher. Overall, these results have important implications to the development of new mechanoresponsive materials., (© 2021 Wiley-VCH GmbH.)