Variable Temperature ROMP: Leveraging Low Ring Strain Thermodynamics To Achieve Well-Defined Polypentenamers

Living-like conditions through ring-opening metathesis polymerization (ROMP) of low ring strain monomers were achieved through temperature variation during the reaction. For a variety of solvents and readily available ruthenium-based catalysts, warm initiation to low conversions followed by immediate thermal quenching and subsequent propagation to high conversions produced polycyclopentene with molar masses close to theoretical and with moderately low dispersities (Đ ≤ 1.3 ± 0.1). Optimization using Grubbs first-generation catalyst and THF as the solvent consistently resulted in narrow dispersities (<1.2) at various molar masses targeted which increased linearly with monomer-to-catalyst ratio. In all cases, intermolecular chain transfer reactions were suppressed at colder temperatures as evidenced by low dispersity for up to 300 min at 0 °C. This approach was extended to 3-cyclopentenol to emphasize the universality of the methodology to other low ring strain monomers with functional group tolerance specific to Ru-based catalysts.