Fast Ring-Opening Metathesis Polymerization of Tricyclic Oxanorbornene Derivatives

A new type of tricyclic oxanorbornene monomer was developed for living ring-opening metathesis polymerization (ROMP). A methyl group located at the endoposition of the oxanorbornene bicycle resulted in polymerization kinetics orders of magnitude slower than the corresponding hydrogen-substituted monomers because of steric effects. Both monomers showed well-controlled molecular weights and excellent dispersities with Grubbs’ third-generation catalyst. The slower endomethyl substituted monomers could even be polymerized in a well-controlled manner using Grubbs’ second-generation catalyst. Investigations of random copolymers demonstrated that the steric hindrance only affects the rate of propagation rather than the rate of initiation. Block copolymers between the fast and slow monomers could be prepared with good molecular weight and dispersity control.