Lignin-Sourced Aromatics for Biodegradable Flexible Copolyesters Mimicking Poly(Butylene Adipate-co- Terephthalate)

Poly(butylene adipate-co-terephthalate) (PBAT) is an important commercial biodegradable flexible copolyester, which is dependent on the fossil-based terephthalates for production. In the present work, two series of PBAT-mimicking copolyesters are synthesized using lignin-sourced aromatic monomers, i.e., methyl 4-(2-hydroxyethoxy) vanillate and methyl 4-(2-hydroxyethoxy) benzoate, aliphatic dimethyl adipate, and 1,4-butanediol. The greenhouse gas emissions associated with the monomer synthesis are investigated by life cycle assessment, and the solvent usage is evaluated. The copolyesters show reasonably high thermal stability, and tunable glass transition temperature and crystallinity upon varying the aromatic-aliphatic ratio. Aerobic biodegradation experiments of the obtained copolyesters over 90 days show a comparable or even faster biodegradation rate compared to the benchmark polymer PBAT. The oxygen gas barrier of the obtained terephthalate-free copolyester films is effectively enhanced compared to that of PBAT, indicating their potential in flexible food packaging applications.