Monomer conversion enables chemical recycling of high-performance plastics and carbon fiber composites without monomer separation

Abstract

High-performance engineering plastics exhibit outstanding mechanical robustness and chemical stability, yet their robust structures often hinder chemical recyclability. Here we report a monomer conversion strategy that enables chemical recycling of high-strength and chemically stable plastics without monomer separation. The plastics are constructed by reversibly cross-linking an amino-terminated poly(aryl ether ketone) macromonomer (PAEK) with its aldehyde-functionalized derivative (PA2EK) through dynamic imine bonds, affording reversibly cross-linked PAEK (rPAEK) networks. The resulting rPAEK plastics exhibit a tensile strength of ~85.8 MPa, a Young’s modulus of ~2.04 GPa, and a high glass transition temperature (Tg) of ~171 °C, with mechanical and thermal properties comparable to those of conventional PAEK. Notably, the imine bonds are confined within hydrophobic and rigid aromatic environments formed by densely packed polymer chains, which effectively suppresses bond dissociation under ambient conditions and endows rPAEK with excellent chemical stability. Chemical recycling of rPAEK proceeds through cleavage of the dynamic imine bonds to generate PAEK and PA2EK, followed by conversion of PA2EK back to PAEK via amide hydrolysis, enabling recovery of a single macromonomer without monomer separation. Integration of rPAEK with carbon fibers (CFs) further affords chemically recyclable CF-rPAEK composites with mechanical properties comparable to those of epoxy-based CF-reinforced composites.