Allylic Epoxides Increase the Strain Energy of Cyclic Olefin Monomers for Ring-Opening Metathesis Polymerization

Ring-opening metathesis polymerization (ROMP) is an effective method for synthesizing high molecular weight, functional polymers, but the technique is limited by its reliance on high ring strain cyclic olefins. As a result, the most common monomers are norbornene derivatives. The reliance on this one molecular framework for efficient ROMP of functionalized materials limits the obtainable properties of ROMP polymers. In this work, we investigate new bicyclic monomers synthesized via epoxidation of commercial dienes. DFT esti-mates of these monomers’ ring strains suggests a particular increase in strain for cyclic olefins containing allylic epoxides. We found that the eight-membered (COO) and five-membered (CPO) cyclic olefins were particularly effective for ROMP. CPO was of especially intriguing due to its excellent polymerizability when compared to the limited reactivity of other five-membered rings. The resulting pol-ymers of both monomers displayed Tgs well below room temperature. Interestingly, poly(3,4-COO) showed both high stereo- and regioregularity while poly(CPO) showed little regularity. Both polymers could be readily modified via post-polymerization ring-opening of the reactive allylic epoxides. With the advantages of high epoxide density in poly(CPO), we see CPO as an exciting new ROMP mon-omer that is easily synthesized, can be polymerized to high conversion at room temperature, and may be facilely modified to yield a wide range of functional materials.