One-Step Compatibilization and Upcycling of Mixed Polyolefins Using a Dynamic Disulfide-Linked Bismaleimide Cross-Linker

Plastic waste management poses significant challenges due to the inefficiency of traditional recycling methods, particularly for mixed polyolefins. Herein, we introduce a bismaleimide-based dynamic cross-linker (DTBMI) featuring disulfide bonds, specifically designed to compatibilize and upcycle polypropylene (PP) and polyethylene (PE) blends. DTBMI offers concise synthesis and reliance on industrially mature radical grafting reactions, enabling a straightforward one-step melt blending process to form a dynamic covalent network across PP and PE phases. This approach markedly improves the compatibility, mechanical performance, and thermal stability of PP/PE blends. With the addition of only 1 phr DTBMI, a PP/PE (50 wt %/50 wt %) blend exhibited a 1.5-fold increase in tensile strength and 4.7-fold higher in toughness. Owing to dynamic disulfide exchange, the network remained reprocessable, retaining over 80% of its mechanical performance after two reprocessing cycles. Furthermore, DTBMI demonstrated strong potential in postconsumer polyolefin recycling, improving toughness by over 40-fold. Collectively, these results underscore DTBMI as a sustainable and industrially viable solution for upcycling mixed polyolefins.