Diazirine‐Functionalized Norbornenes Enable On‐Demand Crosslinking of Ring‐Opening Metathesis Polymerization‐Derived Polymers

ABSTRACT Diazirines are powerful crosslinking motifs that generate highly reactive carbenes upon thermal or photochemical activation, enabling efficient C–H and O–H insertion across diverse polymer systems. Despite this versatility, access to diazirine‐containing polymers has been limited to controlled radical polymerization methods, while their integration into ring‐opening metathesis polymerization (ROMP) platforms has remained unexplored. Here, we report diazirine‐functionalized norbornene monomers that are fully compatible with ROMP, enabling direct incorporation of carbene‐generating crosslinkers into ROMP‐derived materials. Diazirine‐functionalized monomers undergo quantitative conversion under metathesis polymerization to yield well‐defined homopolymers ( Đ < 1.15) with complete diazirine retention. The ability to incorporate diazirines into poly(norbornene)‐based materials is demonstrated with linear copolymers, statistical bottlebrush copolymers, and bottlebrush block copolymers, which all exhibit efficient crosslinking at exceptionally low diazirine loadings (0.1–0.9 wt.%). In microphase‐separated bottlebrush block copolymers, selective placement of diazirines enables crosslinking within targeted domains, stabilizing ordered morphologies and suppressing thermally induced changes upon thermal cycling. Collectively, these results establish diazirine‐functionalized norbornene derivatives as a general platform for integrating efficient crosslinking into precision polymer architectures while also significantly expanding the functional materials landscape accessible via ROMP.