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The consumption of synthetic polymers has ballooned; so has the amount of post-consumer waste generated. The current polymer economy, however, is largely linear with most of the post-consumer waste being either landfilled or incinerated. The lack of recycling, together with the sizable carbon footprint of the polymer industry, has led to major negative environmental impacts. Over the past few years, chemical recycling technologies have gained significant traction as a possible technological route to tackle these challenges. In this regard, olefin metathesis, with its versatility and ease of operation, has emerged as an attractive tool. Here, we discuss the developments in olefin-metathesis-based chemical recycling technologies, including the development of new materials and the application of olefin metathesis to the recycling of commercial materials. We delve into structure–reactivity relationships in the context of polymerization–depolymerization behavior, how experimental conditions influence deconstruction outcomes, and the reaction pathways underlying these approaches. We also look at the current hurdles in adopting these technologies and relevant future directions for the field. 

Fluorinated polymers are important functional materials for a broad range of applications, but the recycling of current fluorinated polymers is challenging. We present the first example of semi-fluorinated polymers that can undergo chemical recycling to form the corresponding monomers under ambient conditions. Prepared through ring-opening metathesis polymerization of functionalized trans -cyclobutane fused cyclooctene ( t CBCO) monomers, these polymers show tunable glass transition temperatures (−2 °C to 88 °C), excellent thermal stability (decomposition onset temperatures >280 °C) and hydrophobicity (water contact angles >90°). The hydrophobicity of the semi-fluorinated polymers was further utilized in an amphiphilic diblock copolymer, which forms self-assembled micelles with a size of ∼88 nm in an aqueous solution. Finally, through an efficient, regioselective para -fluoro-thiol substitution reaction, post-polymerization functionalization of a polymer with a pentafluorophenyl imide substituent was achieved. The ease of preparation, functionalization, and recycling, along with the diverse thermomechanical properties and demonstrated hydrophobicity make the t CBCO-based depolymerizable semi-fluorinated polymers promising candidates for sustainable functional materials that can offer a solution to a circular economy. 

Abstract Helices are unique structures that play important roles in biomacromolecules and chiral catalysis. The mechanochemical unfolding of helical structures has attracted the attention of chemists in the past few years. However, it is limited to a few cases which investigated how the mechanochemical reactivity is impacted by helical configurations. No synthetic helical mechanophore is reported. Herein, a Zn (II) bidipyrrin (BDPR‐Zn) double helix is designed as a potential mechanophore. A cyclic olefin containing a doubly strapped BDPR‐Zn is prepared and used for ring‐opening metathesis polymerization. The corresponding polymer is subjected to pulsed ultrasonication for mechanochemical testing. The sonication results reveal the mechanochemical inertness of BDPR‐Zn unit, which is further supported by force‐coupled simulation. Although no obvious activation is observed, our preliminary results on BDPR‐Zn unit could inspire further rational designs on force‐induced helix unfolding. 

Abstract Chemical recycling to monomer (CRM) is a promising route for transitioning to a circular polymer economy. To develop new CRM systems with useful properties, it is important to understand the effects of monomer structure on polymerization/depolymerization behavior. In earlier work, this group demonstrated chemically recyclable polymers prepared by ring‐opening metathesis polymerization oftrans‐cyclobutane fused cyclooctenes (tCBCO). Here, it is investigated how different substituents on cyclobutane impact the thermodynamics and thermal properties oftCBCO polymers. Introducing additional substituents to acis‐diester functionalizedtCBCO is found to favor the conversion of polymerization; increased polymerization conversion is also observed when thecis‐diester is isomerized into itstranscounterpart. The effects of these structural features on the thermal properties are also studied. These findings can provide important insights into designing next‐generation CRM polymers.