Dynamic Covalent Bonds Bridge Immiscible Polymers

Reversible bond exchange reactions enable dynamic covalent bonds (DCBs) in polymers, which are central to the design of adaptive, recyclable, and reprocessable polymeric materials. Recent experiments have demonstrated that such dynamic crosslinks can effectively compatibilize immiscible polymer blends, opening new opportunities for the upcycling of mixed plastic waste. However, the microscopic mechanisms underlying how DCBs enhance interfacial compatibility remain poorly understood. In this study, we employ density functional theory (DFT) and microkinetic modeling to investigate the kinetics of BERs and the resulting equilibrium bond distributions in polymer blends. Specifically, we analyze three representative bond exchange mechanisms—thioesterification (DCB1), disulfide metathesis (DCB2), and anhydride exchange (DCB3)—in various polymers and their blends. Our results show that while DCB1 and DCB3 can generate both associative and dissociative network topologies, DCB2 predominantly yields dissociative networks. Furthermore, the partitioning of dynamic bonds between the bulk and interfacial regions is found to depend strongly on the polymer chemistry. Notably, the polyethylene–polylactic acid (PE–PLA) blend exhibits a higher fraction of interfacial DCBs, resulting in significantly improved compatibility compared to the polyethylene–polypropylene (PE–PP) blend. Overall, this study provides fundamental insights and design principles for compatibilizing polymer blends through dynamic covalent chemistry, with direct implications for advancing circular polymer economy strategies.