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The development of robust methods for the synthesis of chemically recyclable polymers with tunable properties is necessary for the design of next-generation materials. Polyoxazolidinones (POxa), polymers with five-membered urethanes in their backbones, are an attractive target because they are strongly polar and have high thermal stability, but existing step-growth syntheses limit molar masses and methods to chemically recycle POxa to monomer are rare. Herein, we report the synthesis of high molar mass POxa via ring-opening metathesis polymerization of oxazolidinone-fused cyclooctenes. These novel polymers show <5% mass loss up to 382–411 °C and have tunable glass transition temperatures (14–48 °C) controlled by the side chain structure. We demonstrate facile chemical recycling to monomer and repolymerization despite moderately high monomer ring-strain energies, which we hypothesize are facilitated by the conformational restriction introduced by the fused oxazolidinone ring. This method represents the first chain growth synthesis of POxa and provides a versatile platform for the study and application of this emerging subclass of polyurethanes. 

Carbon dioxide-based polyoxazolidinones (POxa) are an emerging subclass of non-isocyanate polyurethanes for high temperature applications. Current POxa with rigid linkers suffer from limited solubility that hinders synthesis and characterization. Herein, we report the addition of alkyl and alkoxy solubilizing groups to rigid spirocyclic POxa and their poly(hydroxyoxazolidinone) (PHO) precursors. The modified polymers were soluble in up to six organic solvents, enabling characterization of key properties (e.g., molar mass and polymer structure) using solution-state methods. Dehydration of PHO to POxa changed solubility from highly polar to less polar solvents and improved thermal stability by 76–102 °C. The POxa had relatively high glass transition (85–119 °C) and melting (190–238 °C) temperatures tuned by solubilizing group structure. The improved understanding of factors affecting solubility, structure–property relationships, and degradation pathways gained in this study broadens the scope of soluble POxa and enables more rational design of this promising class of materials. 

Abstract Microorganisms play vital roles in modulating organic matter decomposition and nutrient cycling in soil ecosystems. The enzyme latch paradigm posits microbial degradation of polyphenols is hindered in anoxic peat leading to polyphenol accumulation, and consequently diminished microbial activity. This model assumes that polyphenols are microbially unavailable under anoxia, a supposition that has not been thoroughly investigated in any soil type. Here, we use anoxic soil reactors amended with and without a chemically defined polyphenol to test this hypothesis, employing metabolomics and genome-resolved metaproteomics to interrogate soil microbial polyphenol metabolism. Challenging the idea that polyphenols are not bioavailable under anoxia, we provide metabolite evidence that polyphenols are depolymerized, resulting in monomer accumulation, followed by the generation of small phenolic degradation products. Further, we show that soil microbiome function is maintained, and possibly enhanced, with polyphenol addition. In summary, this study provides chemical and enzymatic evidence that some soil microbiota can degrade polyphenols under anoxia and subvert the assumed polyphenol lock on soil microbial metabolism.