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New polymers, properly designed for end-of-life and efficiently formed from renewable carbon, are key to the transition to a more sustainable circular plastics economy. Ring-opening polymerization (ROP) of bicyclic lactones is a promising method for the production of intrinsically recyclable polyesters, but most lactone monomers lack an efficient synthesis route from biobased starting materials, even though this is essential to sustainably account for material loss during the life cycle. Herein, we present the exceptionally rapid and controlled polymerization of a fully biobased tricyclic oxanorbornene-fused γ-butyrolactone monomer ( M1 ). Polyester P( M1 ) was formed in low dispersity (D̵ = 1.2-1.3) and controllable molecular weight up to M n = 76.8 kg mol -1 and exhibits a high glass transition temperature ( T g = 120 °C). The orthogonal olefin and lactone functionalities offer access to a wide range of promising materials, as showcased by postpolymerization modification by hydrogenation of the olefin, which increased polymer thermal stability by over 100 °C. Next to rapid hydrolytic degradation and solvolysis, the poly(oxanorbornene-fused γ-butyrolactone) could be cleanly chemically recycled back to the monomer (CRM), in line with its favorable ceiling temperature ( T c ) of 73 °C. The density functional theory (DFT)-computed Δ H ° of ring-opening with methanol of γ-butyrolactone-based monomers provided a model to predict T c , and the DFT-computed and X-ray crystal structure-derived structural parameters of M1 , hydrogenated analogue M1-H 2 , and regioisomer M2 offered insights into the structural descriptors that cause the high polymerizability of M1 , which is key to establishing structure-property relations.

Diels-Alder (DA) cycloaddition of furanics is emerging as a key transformation in circular chemistry, providing access to highly versatile, biobased platform molecules. Further development of this technology into viable industrial applications faces major challenges, a notorious one being the lack of reactivity of the most readily available furans, i.e. the furfural derivatives. Herein we describe the remarkably-facile intramolecular DA reaction of allyl acetals of different furfurals to efficiently afford formal DA adducts with the atypical, unreactive dienophile allyl alcohol. Our methodology gives access to unprecedented oxanorbornene derivatives in high chemo-, regio- and stereoselectivity, which can be readily diversified into valuable products. This offers the potential of scalable production of renewable chemical building blocks from cheap, bioderived platform molecules., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)