Ring-Opening Metathesis Copolymerization of Cyclopentene Above and Below Its Equilibrium Monomer Concentration

Cyclopentene (C) and norbornene (N) may both be enchained by ring-opening metathesis polymerization (ROMP). N homopolymerizes to essential completion, but C has a significant equilibrium monomer concentration, [C]_eq = 1.17 m at 30 °C. While C cannot homopolymerize below [C]_eq, it can still be enchained in copolymerizations with N. A terminal kinetic model, where one monomer shows depropagation competitive with propagation, well represents experimental data for the “living” ROMP copolymerization of C and N with a Mo-based “Schrock-type” initiator, covering a broad range of monomer feed ratios, both above and below [C]_eq. Incorporating a penultimate unit effect on C depropagation increases the model's accuracy when both the monomers are dilute. Below [C]_eq, polymerization halts when all N is consumed; above [C]_eq, a C homopolymer block forms once all N is consumed. As polycyclopentene may be hydrogenated to linear polyethylene, such copolymerizations offer a facile route to polyethylene-containing block copolymers from a single charge of mixed-monomer feed.