Reprocessable and Chemically Recyclable Polyester Elastomers via a Tandem Ring-Opening Polymerization and Photo-Crosslinking Strategy From Bio-Renewable β-Methyl-δ-Valerolactone

Due to the lack of effective physical reprocessing or chemical recovery capabilities, thermosetting polymers face long-term post-disposing problems. The introduction of dynamic covalent bonds can effectively combine reprocessing ability with typical robust properties of thermosetting polymer. However, after multiple reprocessing treatments, thermosets often suffer significant decrease in mechanical properties, so the chemical recycling and reuse is crucial and necessary for the sustainable development of thermosetting polymers. Herein, a series of polyesters PβMδVL-TA with mono- or bis-terminal cyclic disulfide bond was first synthesized via esterification between terminal hydroxyl of PβMδVL and carboxyl of thioctic acid (TA). Then, the thermosetting elastomer with both physical reprocessability and chemical recyclability was prepared by simple UV-triggered ring-opening polymerization of cyclic disulfide. By regulating cross-linking sites and the molecular weight of the mono- or bis-PβMδVL-TA, such polyester elastomers exhibit good tensile strength and elasticity with elastic recovery can reach 98% after 10 cycles. Furthermore, the dynamic reaction of disulfide bonds induced by hot pressing and UV light enables multiple reprocessing of cross-linked elastomers. Remarkably, the efficient chemical recycling of the elastomers was achieved to recover pristine βMδVL monomer with 90% yield in the presence of ZnCl₂ as the catalyst at 130°C.