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<p>To enhance the properties of bio-based polyesters, enabling them to more closely mimic the characteristics of terephthalate-based materials, a series of aliphatic-aromatic copolyesters (P<sub>1</sub>–P<sub>4</sub>) were synthesized <i>via</i> melt polycondensation. Diester monomers M and N were synthesized <i>via</i> the Williamson reaction, using lignin-derived 2-methoxyhydroquinone, methyl 4-chloromethylbenzoate, and methyl chloroacetate as starting materials. Hydroquinone bis(2-hydroxyethyl)ether (HQEE) and 1,4-cyclohexanedimethanol (CHDM) were employed as cyclic segments, while 1,4-butanediol (BDO) and 1,6-hexanediol (HDO) served as alkyl segments within the copolymer structures. The novel copolyesters exhibited molecular weights (<i>M</i><sub>w</sub>) in the range of 5.25×10<sup>4</sup>–5.87×10<sup>4</sup> g/mol, with polydispersity indices spanning from 2.50–2.66. Evaluation of the structural and thermomechanical properties indicated that the inclusion of alkyl segments induced a reduction in both crystallinity and molecular weight, while significantly improving the flexibility, whereas cyclic segments enhanced the processability of the copolyesters. Copolyesters P<sub>1</sub> and P<sub>2</sub>, due to the presence of rigid segments (HQEE and CHDM), displayed relatively high glass transition temperatures (<i>T</i><sub>g</sub>&gt;80 °C) and melting temperatures (<i>T</i><sub>m</sub>&gt;170 °C). Notably, P<sub>2</sub>, incorporating CHDM, exhibited superior elongation properties (272%), attributed to the enhanced chain mobility resulting from its <i>trans</i>-conformation, while P<sub>1</sub> was found to be likely brittle owing to excessive chain stiffness. Biodegradability assessment using earthworms as bioindicators revealed that the copolyesters demonstrated moderate degradation profiles, with P<sub>2</sub> exhibiting a degradation rate of 4.82%, followed by P<sub>4</sub> at 4.07%, P<sub>3</sub> at 3.65%, and P<sub>1</sub> at 3.17%. The higher degradation rate of P<sub>2</sub> was attributed to its relatively larger d-spacing and lower toxicity, which facilitated enzymatic hydrolytic attack by microorganisms. These findings highlight the significance of optimizing the structural chain segments within aliphatic-aromatic copolyesters. By doing so, it is possible to significantly enhance their properties and performance, offering viable bio-based alternatives to petroleum-based polyesters such as polyethylene terephthalate (PET).</p>

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Biobased Polyesters Derived from 2-Methoxyhydroquinone: Impact of Cyclic and Alkyl Chain Segments on Their Thermomechanical Properties, Biodegradability, and Ecotoxicity

  • 期刊论文

  • 发表日期：

    2025年6月18日

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  • Hao-Ming Xu,
  • Zheng-Zai Cheng,
  • Zi-Ting Zhou,
  • Lesly Dasilva Wandji Djouonkep,
  • Mario Gauthier

摘要

To enhance the properties of bio-based polyesters, enabling them to more closely mimic the characteristics of terephthalate-based materials, a series of aliphatic-aromatic copolyesters (P1–P4) were synthesized via melt polycondensation. Diester monomers M and N were synthesized via the Williamson reaction, using lignin-derived 2-methoxyhydroquinone, methyl 4-chloromethylbenzoate, and methyl chloroacetate as starting materials. Hydroquinone bis(2-hydroxyethyl)ether (HQEE) and 1,4-cyclohexanedimethanol (CHDM) were employed as cyclic segments, while 1,4-butanediol (BDO) and 1,6-hexanediol (HDO) served as alkyl segments within the copolymer structures. The novel copolyesters exhibited molecular weights (Mw) in the range of 5.25×104–5.87×104 g/mol, with polydispersity indices spanning from 2.50–2.66. Evaluation of the structural and thermomechanical properties indicated that the inclusion of alkyl segments induced a reduction in both crystallinity and molecular weight, while significantly improving the flexibility, whereas cyclic segments enhanced the processability of the copolyesters. Copolyesters P1 and P2, due to the presence of rigid segments (HQEE and CHDM), displayed relatively high glass transition temperatures (Tg>80 °C) and melting temperatures (Tm>170 °C). Notably, P2, incorporating CHDM, exhibited superior elongation properties (272%), attributed to the enhanced chain mobility resulting from its trans-conformation, while P1 was found to be likely brittle owing to excessive chain stiffness. Biodegradability assessment using earthworms as bioindicators revealed that the copolyesters demonstrated moderate degradation profiles, with P2 exhibiting a degradation rate of 4.82%, followed by P4 at 4.07%, P3 at 3.65%, and P1 at 3.17%. The higher degradation rate of P2 was attributed to its relatively larger d-spacing and lower toxicity, which facilitated enzymatic hydrolytic attack by microorganisms. These findings highlight the significance of optimizing the structural chain segments within aliphatic-aromatic copolyesters. By doing so, it is possible to significantly enhance their properties and performance, offering viable bio-based alternatives to petroleum-based polyesters such as polyethylene terephthalate (PET).