Dynamic crosslinking of thermoplastics via perfluorophenyl nitrene C–H insertion to form recyclable thermosets

Covalent adaptable networks (CANs) are polymers crosslinked via dynamic covalent bonds (DCBs), endowing the networks with both thermoset-like stability and thermoplastic-like recyclability. Although post-polymerization crosslinking of thermoplastics is an efficient strategy to form CANs, the process is non-trivial, especially for poly(olefins) that have low functionality and a fully hydrocarbon backbone. Herein, we introduce perflurophenyl azide-based nitrene crosslinkers to install disulfide, imine, and acetal DCBs into poly(olefins) and other thermoplastics, thereby converting them into CANs. Crosslinking was effective for a wide range of thermoplastics, imparting both dimensional and solvent stability. The resultant CANs could also exhibit enhanced mechanical performance, such as doubling of tensile toughness and self-healing ability. Unlike traditional thermosets, the DCBs enabled these CANs to be chemically and/or mechanically recycled multiple times. This methodology has the advantage of utilizing existing and even post-consumer plastic blends as starting materials, improving their thermo-mechanical properties while maintaining recyclability of the synthesized CANs.