Ring-Opening Metathesis Polymerization of Caged FLP Monomers and Uncaged Alkene Macromonomers

Frustrated Lewis pairs (FLPs) are promising motifs for responsive polymeric materials, but their unique reactivity renders access to FLP-containing polymer systems challenging. We previously described a strategy for "caging" FLPs as FLP-alkene adducts, which enabled the synthesis of vinyl addition polynorbornenes bearing caged FLP functionality; however, the steric bulk of the caged FLP substituents prevented controlled polymerization. Here, we report the synthesis of well-defined caged FLP polymers via ring-opening metathesis polymerization (ROMP). To mitigate the steric demands of the bulky FLP substituents, we designed a monomer in which the caged FLP unit is spatially separated from the polymerizable alkene via a rigid alicyclic framework. This design permits living-like ROMP with Grubbs-type initiators to afford homopolymers and copolymers with predictable molar mass, low dispersity, tunable caged FLP content, and sequence control. Photochemical uncaging releases a persistent molecular FLP while simultaneously generating strained cyclic alkenes along the polymer backbone. The resulting polymers function as photolatent macromonomers that are amenable to subsequent olefin metathesis, enabling controlled cross-linking and copolymer network formation. This ROMP-uncaging-ROMP strategy provides temporal control over FLP reactivity and expands access to responsive FLP-containing polymer architectures.