Lignin-inspired aromatic–aliphatic copolyesters with tunable thermomechanical properties for potential teaching material aid

The development of sustainable polyester materials that simultaneously achieve high mechanical performance, thermal stability, and environmental compatibility remains challenging because of the inherent tradeoff between rigid aromatic structures and flexible aliphatic segments. Herein, a lignin-inspired aromatic diol monomer, [1,4-phenylenebis(methyleneoxymethylene-4,1-phenylene)]dimethanol (PMBD), was synthesized from 4-(hydroxymethyl)phenol and subsequently polymerized with dimethyl 4,4′-((1,4-phenylenebis(methylene))bis(oxy))dibenzoate (DPMD) and different aliphatic diols to construct sustainable aliphatic–aromatic copolyesters. The effect of aliphatic spacer length was systematically investigated by comparing the BDO-containing copolyester PMDB with the ODO-containing copolyester PMDH. PMDB exhibited higher rigidity and thermal resistance with a tensile strength of 67 MPa, Tg of 85 °C, and Tm of 180 °C, while PMDH exhibited enhanced ductility, with a tensile strength of 54 MPa, a Tg of 56 °C, and an elongation at break of 300%. This increased chain mobility contribute to greater deformability, providing preliminary materials basis for teaching material applications. Both copolyesters showed high thermal stability (Td,5% = 340–370 °C) and progressive soil-associated mass loss during 30 wk of soil burial. These findings demonstrate that aliphatic-spacer engineering provides a route to tune the thermomechanical response and soil-exposure behavior of lignin-inspired aromatic–aliphatic copolyesters.