Tailoring biobased aliphatic polyesters for high Tg, scalable production, processability, biodegradability, and closed-loop chemical recyclability

Fully bio-based spirocyclic monomers with high reactivity and thermal stability in polycondensations, and scalable production from low-cost reactants are attractive alternatives to replace fossil-based terephthalate monomers. To this end, we carefully design and synthesize a dicarboxylate ester monomer with a spiroacetal structure from bio-based pentaerythritol and glyoxylic acid. Polycondensations of the spiro-monomer with various potentially bio-based diols yield a family of fully amorphous and transparent film- and fiber-forming polyesters with M n = 15–23 kg mol −1 and glass transition temperatures between 27 and 127 °C. A 1,6-hexanediol-derived polyester film shows greatly improved oxygen barrier properties compared with commercial polyester materials. The ester bonds in the polyesters can be selectively cleaved under mildly acidic, or even neutral, catalyst-free methanolysis at 50 °C, while keeping the spiroacetal groups intact. We demonstrate that it is possible to conveniently and selectively depolymerize the polyesters by methanolysis, even in the presence of mixed plastic waste, followed by recovery and re-polymerization of the monomers to obtain chemically recycled polyesters with properties comparable to the original materials. Moreover, biochemical oxygen demand measurements show 59 % degradation of a selected polyester after 90 days at 50 °C in a composting environment, nearly 20 % higher than the PBAT control sample. • Spiroacetal dicarboxylate monomer from pentaerythritol and glyoxylic acid • Fully bio-based with high reactivity and thermal stability • Polycondensations to compostable amorphous polyesters with T g s up to 127 °C • Excellent mechanical and oxygen barrier properties • Efficient chemical recycling via mildly acidic or catalyst-free methanolysis at 50 °C