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Polymer blends offer a cost-effective way to create new materials with enhanced properties. However, blending different polymers often results in phase separation with weak interfacial adhesion, leading to inferior mechanical properties. Given that high-density polyethylene (HDPE) and isotactic polypropylene (iPP) are the largest volume polymers, there is significant interest in developing blends of these materials. Applying a singlet nitrene-facilitated dynamic crosslinking method recently developed in our lab, in this study we prepared a series of HDPE/iPP blends across a range of compositions with enhanced compatibility and tunable thermomechanical properties. By incorporating a small amount of a dynamic crosslinker featuring a siloxane core and bis-aromatic sulfonyl azides (bis-ASA) into varying compositions of HDPE and iPP, we achieve significant improvements in the compatibility. AFM and SEM imaging analyses reveal that the compatibilized blends exhibit superior homogeneity compared to control blends. Additionally, these blends show significant improvements in elongation at break, toughness, and oxidative stability. The dynamic crosslinking further enhances the blends’ creep resistance while retains reprocessability, paving the way for the development of tailorable polymer blends for various applications. 

Abstract Creating a sustainable economy for plastics demands the exploration of new strategies for efficient management of mixed plastic waste. The inherent incompatibility of different plastics poses a major challenge in plastic mechanical recycling, resulting in phase‐separated materials with inferior mechanical properties. Here, this study presents a robust and efficient dynamic crosslinking chemistry that effectively compatibilizes mixed plastics. Composed of aromatic sulfonyl azides, the dynamic crosslinker shows high thermal stability and generates singlet nitrene species in situ during solvent‐free melt‐extrusion, effectively promoting C─H insertion across diverse plastics. This new method demonstrates successful compatibilization of binary polymer blends and model mixed plastics, enhancing mechanical performance and improving phase morphology. It holds promise for managing mixed plastic waste, supporting a more sustainable lifecycle for plastics. 

We elucidate the mechanisms of chemically driven self-assembly processes, demonstrating how synchronous assembly–disassembly reactions can stabilize transient structures and create morphologies that differ from conventional assemblies.