Dynamic crosslinking compatibilizes immiscible mixed plastics

The global plastics problem is a trifecta, greatly affecting environment, energy and climate^1-4. Many innovative closed/open-loop plastics recycling or upcycling strategies have been proposed or developed^5-16, addressing various aspects of the issues underpinning the achievement of a circular economy^17-19. In this context, reusing mixed-plastics waste presents a particular challenge with no current effective closed-loop solution²⁰. This is because such mixed plastics, especially polar/apolar polymer mixtures, are typically incompatible and phase separate, leading to materials with substantially inferior properties. To address this key barrier, here we introduce a new compatibilization strategy that installs dynamic crosslinkers into several classes of binary, ternary and postconsumer immiscible polymer mixtures in situ. Our combined experimental and modelling studies show that specifically designed classes of dynamic crosslinker can reactivate mixed-plastics chains, represented here by apolar polyolefins and polar polyesters, by compatibilizing them via dynamic formation of graft multiblock copolymers. The resulting in-situ-generated dynamic thermosets exhibit intrinsic reprocessability and enhanced tensile strength and creep resistance relative to virgin plastics. This approach avoids the need for de/reconstruction and thus potentially provides an alternative, facile route towards the recovery of the endowed energy and materials value of individual plastics.