Thermally Self-Healing Polymeric Materials: The Next Step to Recycling Thermoset Polymers?

TLDR

The authors developed thermally self‑healing polymeric materials based on furan‑functionalized alternating thermosetting polyketones and bis‑maleimide using a Diels–Alder/retro‑Diels–Alder reaction sequence. PK‑furan is synthesized under mild conditions via a Paal–Knorr reaction of polyketones with furfurylamine, and the resulting material undergoes reversible DA/RDA chemistry for self‑healing. The highly cross‑linked polymers fully recover fracture strength upon thermal remending, the process can be repeated without loss of mechanical properties, and the simple, broadly applicable synthesis offers complete recyclability and reworkability, advancing cradle‑to‑cradle thermoset plastics.

Abstract

We developed thermally self-healing polymeric materials on the basis of furan-functionalized, alternating thermosetting polyketones (PK-furan) and bis-maleimide by using the Diels−Alder (DA) and Retro-Diels−Alder (RDA) reaction sequence. PK-furan can be easily obtained under mild conditions by the Paal−Knorr reaction of the polyketones with furfurylamine. The highly cross-linked polymers can be thermally remended to complete recovery in fracture loading, whereas the remending process can be repeated multiple times without any loss in mechanical properties. It is found that the achieved self-healing ability of this easily accessible system provides full recyclability and reworkability, which often is perceived to be difficult or impossible for thermosetting polymers. The simplicity of the synthesis, the broad range of available polyketone precursors, and the striking healing ability (kinetics and efficiency of mechanical properties recovery) of this system could expand the scientific understanding of self-healing materials and introduce the cradle-to-cradle concept for thermoset-based plastics and composites.