Screening Bio-Based Furanoate Copolyesters for Crystallinity and Biodegradability

Furanoate polyesters derived from bio-based 2,5-furandicarboxylic acid (FDCA) show promise as sustainable alternatives to traditional petroleum-based poly(ethylene terephthalate) (PET) for various engineering applications, such as fibers, bottles, and films. However, these materials exhibit a trade-off between biodegradability and the crystallinity required for such uses: some furanoate homopolyesters are biodegradable but completely amorphous, whereas others are crystalline but not biodegradable, limiting their appeal. To address this shortcoming, copolymerization was pursued as a strategy to investigate whether small amounts of comonomer incorporation could improve biodegradability while retaining or even enhancing the crystallinity needed for engineering applications. A library of over 200 unique furanoate copolyester chemistries was synthesized. Crystallinity and biodegradability were assessed using partially automated wide-angle X-ray scattering (WAXS) and clear-zone biodegradation assays, respectively. Most copolyesters show very similar scattering patterns to their homopolyester counterparts, although the percent crystallinity generally decreases at higher levels of comonomer incorporation. In contrast, biodegradability is highly sensitive to the specific choice of comonomer and level of incorporation in the copolymer, with copolyesters derived from biodegradable homopolyesters losing their biodegradability even at comonomer contents as low as 13%. Most notably, two furanoate copolyester compositions stand out as the most promising candidates based on their crystallinity (>20%) and biodegradability via the clear-zone mechanism: copolyesters of poly(ethylene furanoate) with 1,2-propanediol (P12PF-PEF) and triethylene glycol (PTEF-PEF).