Reconfigurable and recyclable High-Temperature triple shape memory polymers from upcycling of commercial Nylon 6 vitrimers

This study introduces the development of high-temperature shape memory polymers (HTSMPs) with triple shape memory properties, achieved through the vitrimerization of commercial Nylon 6. These materials exhibit exceptional reprocessability, reconfigurability, and recyclability. Polyamide vitrimer (PAV) was synthesized via solid-state polymerization (SSP) using tris(2-aminoethyl)amine (TAA) and sebacic acid (SA) as the crosslinker salt, with scandium(III) triflate (Sc(OTf)₃) serving as the catalyst to facilitate dynamic covalent bond exchange. The thermal and viscoelastic properties of the PAVs were systematically tuned by varying the crosslinker and catalyst concentrations. Among the formulations, PAV-5/1 (containing 5 and 1 mol% crosslinker salt and catalyst, respectively) exhibited excellent thermal stability and retained nearly its original tensile strength and modulus after multiple reprocessing cycles, demonstrating its robust mechanical reprocessability. Dynamic mechanical analysis (DMA) revealed high shape fixity and recovery ratios, with consistent triple shape memory behavior under harsh high-temperature conditions. The reconfigurability of PAV-5/1 was demonstrated through reshaping its permanent structure via transamidation reactions, while its recyclability was validated by successfully reprocessing films from powder. These findings highlight the potential of PAV-5/1 as a multifunctional HTSMP for advanced applications, such as aerospace structures and high-temperature actuators, while contributing to sustainability efforts through polymer upcycling.