A Greener Approach to 2,5‐Furandicarboxylate Macrocycles and their Entropically Driven Ring Opening Polymerization

Thermoplastic polyesters (PEs), with their versatile properties, are indispensable in everyday life. However, increasing concerns about the environmental impact of fossil-based polymers have driven research into renewable alternatives. Among bio-based polymers, furan-derived PEs such as poly(ethylene furanoate) (PEF) have garnered significant attention. The synthesis of PEF, as well as other similar 2,5-furandicarboxylic acid (FDCA)-based polymers, is mainly based on bulk polycondensation (PC) that in general requires elevated temperatures and low pressure, making the process energy-intensive and vulnerable to thermo-oxidative degradation. In this view, entropically driven ring opening polymerization (ED-ROP) might represent an interesting potential alternative since it requires milder conditions and is intrinsically more atom economic. From these premises, this work focuses on developing an alternative synthetic strategy to bio-based PEs through ED-ROP of macrocycles derived from FDCA dimethyl ester (FDME). These macrocycles were prepared by reacting FDME with diols via pseudo-high dilution condensation (PHDC) using dibutyltin(IV) oxide as a catalyst and cyclopentyl methyl ether as a recyclable green solvent. Isolation of the pure macrocycles is achieved by simple crystallization from the reaction mixture. Subsequent ROP of pure macrocycles is investigated as a viable route to prepare the related PEs in mild reaction conditions.