Dynamic Diels-Alder Block Copolymers for Compatibilization of Multicomponent Polymer Blends.

Mechanical recycling of mixed plastic waste is limited by the inherent immiscibility of different polymers, which causes phase separation and degraded mechanical properties. Preformed block copolymers can compatibilize immiscible blends, but this strategy becomes synthetically impractical for multicomponent mixtures because each pairwise polymer interface typically requires a distinct compatibilizer. Here, we introduce a dynamic compatibilization strategy in which Diels-Alder (DA) homopolymers undergo thermally induced exchange to generate block copolymers in situ. Using a difunctional RAFT initiator bearing a dicyclopentadiene (DCPD) motif, we synthesized well-defined DA-functionalized homopolymers by photoiniferter RAFT polymerization under 365 nm irradiation. After confirming the dynamic exchange of the DA homopolymers, the resulting equilibrated block copolymers were used directly to compatibilize binary, ternary, and quaternary polymer blends, leading to substantial domain-size reductions observed by AFM and SEM. In melt-processed blends, the morphology improvement produced substantial enhancements in mechanical performance, with toughness increase of up to 550%. This proof-of-concept study establishes dynamic DA homopolymers as an adaptable platform that generates block copolymers in situ for compatibilizing complex polymer mixtures relevant to mixed-plastic waste recycling.