Harnessing the β ‐Silicon Effect for Radical Cyclopolymerization: Direct Access to Si‐Containing Cyclic Olefin Polymers

Cyclic olefin polymers (COPs) are important functional materials with extensively studied properties and syntheses. By contrast, silicon‐containing cyclic olefin polymers (Si‐COPs)—promising alternatives to conventional COPs—remain largely unexplored. Herein, we report a radical cyclopolymerization strategy enabled by the β ‑silicon effect for the efficient synthesis of Si‐COPs. Harnessing the β ‐silicon effect to stabilize radical intermediates suppresses the inherent chain transfer tendency of non‐conjugated diene monomers in radical cyclopolymerization and enables the control of the cyclization selectivity. Density functional theory (DFT) calculations provide mechanistic insight into the polymerization pathway. The resulting Si‐COPs serve as versatile platforms for post‐polymerization modification and undergo controlled degradation under mild conditions. Furthermore, cross‐linked Si‐COPs fabricated via thiol–ene chemistry exhibit optical properties comparable to those of commercial COPs, together with outstanding adhesion performance.