7-Oxa-2,3-diazanorbornene (ODAN): A One-Step Accessible Monomer for Living ROMP to Produce Backbone-Biodegradable Polymers

Traditional ring-opening metathesis polymerization (ROMP) reactions exhibit broad functional group compatibility and precise control over polymer architectures, albeit with non-biodegradable backbones. Recent progress has resulted in a series of biode-gradable ROMP products with diverse cleavable functional groups, yet the majority of the monomers display moderate to low ring strain, which restricts their living polymerization reactivity. In this study, a novel category of readily available 7-oxa-2,3-diazanorbornenes (ODAN) is presented, which exhibits the highest ring strain (22.8 kcal/mol) compared to existing degradable ROMP monomers. This trait endows ODAN with the ability to perform living polymerization reactions, generating narrowly dis-persed homopolymers, block copolymers, and statistical copolymers with various cyclic olefin comonomers, thereby enabling pre-cise control over distribution of the biodegradable functional groups. Additionally, the resultant polymers comprise directly con-nected allyl hemiaminal ether and urethane units, which are hydrolysable at controllable rates. Thus, these well-defined, structure-tunable, and backbone-biodegradable ROMP polymers are applied as nano-etching materials and biodegradable delivery carriers.