A versatile approach for the synthesis of degradable polymers via controlled ring-opening metathesis copolymerization

Norbornene derivatives (NBEs) are common monomers for living ring-opening metathesis polymerization and yield polymers with low dispersities and diverse functionalities. However, the all-carbon backbone of poly-NBEs is non-degradable. Here we report a method to synthesize degradable polymers by copolymerizing 2,3-dihydrofuran with NBEs. 2,3-Dihydrofuran rapidly reacts with Grubbs catalyst to form a thermodynamically stable Ru Fischer carbene—the only detectable active Ru species during copolymerization—and the addition of NBEs becomes rate determining. This reactivity attenuates the NBE homoaddition and allows uniform incorporation of acid-degradable enol ether linkages throughout the copolymers, which enables complete polymer degradation while maintaining the favourable characteristics of living ring-opening metathesis polymerization. Copolymerization of 2,3-dihydrofuran with NBEs gives low dispersity polymers with tunable solubility, glass transition temperature and mechanical properties. These polymers can be fully degraded into small molecule or oligomeric species under mildly acidic conditions. This method can be readily adapted to traditional ring-opening metathesis polymerization of widely used NBEs to synthesize easily degradable polymers with tunable properties for various applications and for environmental sustainability. Degradable polymers are important for technological applications and sustainability, but they remain difficult to access via ring-opening metathesis polymerization (ROMP). Now, commercial 2,3-dihydrofuran is shown to be an effective ROMP comonomer for various norbornenes. This copolymerization generates new acid-degradable polymers with controlled molecular weights, different functionalities and tunable properties.