Self-Healable Polyurethane Elastomer Based on Dual Dynamic Covalent Chemistry Using Diels–Alder “Click” and Disulfide Metathesis Reactions

Functional polyurethanes have several important advanced applications. In this investigation, a dual-functional polyurethane (PU) elastomer having disulfide as well as furfuryl functionality was developed. For this purpose, a functional diol having furfuryl and disulfide functionality was synthesized and used as a chain extender for the synthesis of a PU elastomer based on polycaprolactone (PCL) diol and 4,4′-methylenebis (phenyl diisocyanate) (MDI). This dual functional PU elastomer was cross-linked using a bismaleimide (BM) via the Diels–Alder (DA) reaction with the furfuryl pendant group in PU. This dual functional PU having thermoreversible DA linkage and disulfide linkage showed excellent tensile strength (σ = 39.5 MPa) and, importantly, good self-healing characteristics (self-healing efficiency, Eσ ≈ 97%). This healable PU having a thermoresponsive as well as a double dynamic covalent system based on the DA reaction and the disulfide metathesis reaction will have potential applications in specialty paints, coatings, and various advanced materials.