Strong self-healing close-loop recyclable vitrimers via complementary dynamic covalent/non-covalent bonding

Abstract

• A strong and room-temperature self-healing DCNC/50PEDA vitrimer is created; • The room-temperature self-healing efficiency of DCNC/50PEDA reaches 96.0%; • The tensile strength of DCNC/50PEDA is up to 36.0 MPa; • DCNC/50PEDA shows desired closed-loop recyclability; • DCNC/50PEDA features exceptional adhesion performances and fire retardancy. Epoxy vitrimers represent a new class of high-performance sustainable resins because of their desired mechanical and thermally malleable properties. Unfortunately, existing epoxy vitrimers cannot self-heal at room temperature (R.T.) due to the trade-off between mechanical robustness, recyclability, and the ‘frozen’ state of vitrimer networks at R.T. Herein, a high-performance hyperbranched epoxy vitrimer (DCNC/50PEDA) via curing bis(2,3-epoxypropyl) cyclohex-4-ene-1,2-dicarboxylate (DCNC) with 50 wt% of a phosphorus/silicon-containing polyethyleneimine (PEDA) at R.T., and the key to this design lies in rationally integrating complementary dynamic non-covalent hydrogen-bonding and π-π stacking and covalent β-hydroxy ester bonds into the high-mobility branched units of the DCNC/50PEDA network. This design endows the vitrimer with a room-temperature self-healing efficiency up to 96.0 %, high mechanical strength reaching 36.0 MPa, and desired closed-loop recyclability. Moreover, its strong adhesion to a variety of substrates and exceptional fire retardancy, e.g., a limiting oxygen index of 39.0 % and a desired UL-94 V-0 rating, make it an outstanding fire-retardant coating for flammable substrates, such as wood. Such a performance portfolio enables DCNC/50PEDA to outperform existing self-healing polymer and vitrimers counterparts. This work establishes a promising complementary dynamic design protocol for creating self-healing, strong, recyclable, and fire-safe polymers by integrating dynamic non-covalent interactions and covalent bonds, which hold great real-world applications in industries, such as bulk materials, coatings, and adhesives.