7-Oxa-2,3-Diazanorbornene: A One-Step Accessible Monomer for Living Ring-Opening Metathesis Polymerization 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 biodegradable 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 dispersed homopolymers, block copolymers, and statistical copolymers with various cyclic olefin comonomers, thereby enabling precise control over distribution of the biodegradable functional groups. Additionally, the resultant polymers comprise directly connected allyl hemiaminal ether and urethane units, which are hydrolyzable at controllable rates. Thus, these well-defined, structure -tunable, and backbone -biodegradable ROMP polymers are applied as nanoetching materials and biodegradable delivery carriers.