Structure-Guided Upcycling of Polyamide 6 Waste into Ultra-Strong Adhesives

Abstract Upcycling polymer waste, especially polyamide 6 (PA6), remains challenging because it is difficult to simultaneously exploit its intrinsic structural advantages and meet the performance requirements of high-value applications. Herein, we propose a structure-guided upcycling strategy for the fabrication of high-performance adhesives through the partial depolymerization of PA6 via glycolysis followed by directed molecular reconstruction. By incorporating rigid aromatic moieties and flexible polyether soft segments into the reconstructed polymer network, a compatible and controllable polymerization system for PA6 glycolysates was established. This structural design not only preserved high cohesive strength within the adhesive matrix but also enhanced interfacial interactions with diverse substrates, thereby enabling excellent bonding performance. The resulting adhesives exhibited outstanding adhesion strength toward various materials. In particular, the lap-shear strength toward different metals exceeded 15 MPa, with the highest value of 22.9 MPa achieved on iron substrates. In addition, the adhesive displayed desirable practical features, including transparency, solubility, reusability, and stability under various aqueous conditions. Overall, the adhesive performance and multifunctionality of the obtained adhesives compare favorably with those of previously reported polyamide-based adhesives. This work provides a practical and efficient route for the high-value upcycling of polyamide waste.