Isodimorphic Poly(trimethylene adipate- <i>co</i> -terephthalate) Copolyesters with Good Spinnability and Closed-Loop Chemical Recycling

The disposal of postconsumer textiles presents a critical challenge to environmental sustainability, while most existing biodegradable copolyesters exhibit poor spinnability. Therefore, developing sustainable copolyesters that combine robust processability, degradability, and closed-loop recyclability is essential for advancing ecofriendly fiber materials. Herein, we synthesized the high-molecular-weight poly(trimethylene adipate-co-terephthalate) (PTAT) copolyesters with varying compositions through esterification and melt-polycondensation. The relationships between copolyester composition, crystalline structure and properties, spinnability, and chemical recyclability were systematically investigated. The copolyesters exhibit isodimorphic crystallization features, showing the pseudoeutectic region at the trimethylene adipate fraction of 0.79–0.88. The crystalline structure of copolyesters transforms from poly(trimethylene terephthalate)-type to poly(trimethylene adipate)-type crystals at the pseudoeutectic region. The incorporation of adipic acid units reduces the crystallizability and crystallinity of copolyesters while simultaneously enhancing the toughness and degradability. Importantly, these copolyesters show good spinnability, allowing successful fiber fabrication through melt-spinning, and also demonstrate closed-loop chemical recyclability through efficient depolymerization into monomers under mild conditions. This study offers deep insights into the molecular design of sustainable copolyesters with good spinnability, degradability, and recyclability.