Upcycling Poly(ethylene terephthalate) Into High-Efficient Epoxy Toughener: Hyperbranched Oligomer Induced Nano-Structural Heterogeneities.

The post-consumer recycling efficacy of poly(ethylene terephthalate) (PET) has attracted considerable attention. Current chemical recycling of PET predominantly targets monomers, specialty chemicals, and functional materials, yet faces hurdles of costly purification/decolorization and limited market capacity. Here, we report an upcycling paradigm to directly transfer waste PET into highly efficient epoxy tougheners. Through a one-pot process, PET is converted into hyperbranched oligomers (HBO) bearing a compact architecture and abundant terminal hydroxyl groups. This unique structure enables uniform dispersion and covalent integration into the epoxy network during curing, resulting in the formation of chemically seamless and homogeneous rigid nano-structural heterogeneities. And these nano-structural heterogeneities act as stress concentrators that activate localized plastic deformation, promote crack deflection and bridging, and induce microcracking, collectively establishing a multi-scale energy dissipation network, rather than the cavity-induced shear deformation process characteristic of conventional hyperbranched polymers. Remarkably, merely 0.3 wt.% incorporation enhances impact strength by 98.9% without compromising intrinsic processability, mechanical and thermal stability. Moreover, this method demonstrates strong feedstock versatility and has been validated at the kilogram scale, offering a viable and integrated pathway for high-value plastic circularity.