Free-Radical Ring-Opening Polymerization

Although the ionic ring-opening polymerization of heterocyclic compounds, such as ethylene oxide, tetrahydrofuran, ethylen-imine, β-propiolactone, and caprolactam, as well as the Ziegler-Natta ring-opening of cyclic olefins, such as cyclopentene and norbornene, are well known, free radical ring-opening polymerizations are rather rare. The few examples that are reported in the literature involve cyclopropane derivatives or highly strained bi-cyclic olefins. For example, Takahashi [l] studied the free radical polymerization of vinylcyclopropane and reported that the cyclopropane ring opened to give a polymer containing about 80% 1,5-units and about 20% of undetermined structural units.