Investigating the effects of bulky allylic substituents on the regioregularity and thermodynamics of ROMP on cyclopentene

A series of allylic trialkylsiloxy-substituted cyclopentene monomers are examined for their ROMP thermodynamic values and the amount of head-to-tail (HT) regioregular insertion they supply to their respective polymers. With the goal of finding the best of both worlds, a new monomer is found to polymerize with up to 56% conversion at −10 °C and an unprecedented level of HT insertion (97%). This discovery allows continuation of this monomer towards highly isotactic and regioregular polypentenamers.