Bio-sourced methylenediphenol-aliphatic copolyesters: Synthesis from diester monomer to high-performance copolyesters

In this study, an aromatic diester monomer (M) was synthesized from lignin-derived 4,4-bis(4-hydroxyphenyl)methane and methyl 4-(chloromethyl)benzoate. Subsequently, a series of methylenediphenol-aromatic copolyesters (P1–P4) were prepared via polycondensation of monomer M, hydroquinone bis(2-hydroxyethyl) ether as a chain extender, and varying flexible aliphatic diacids (1,4-succinic acid, 1,6-adipic acid, 1,8-suberic acid, or 1,12-dodecanedioic acid). The structure-property relationships were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The copolyesters demonstrated weight-average molecular weights (Mw) ranging from 43,200–50,100 g/mol, glass transition temperatures (Tg) from 63–97 °C, and melting points (Tm) from 152–183 °C, with 5% weight loss temperatures (Td, 5%) varying from 326–353 °C. High yield strength (55–71 MPa) and excellent elongations at break (253–319%) were obtained owed to the balanced aromatic-aliphatic ratio components. Furthermore, the accessible flexible chain segments promote copolyesters degradation with a maximum mass loss of 5.3% after 32 wk of soil incubation, with survival rate of earthworms surpassing 80% when exposed to high copolyester concentrations after 14 days. Overall, the study highlights the synthesis-to-property relationship from thermomechanical, ecotoxicity, and biodegradability properties of copolyesters derived from lignin.