Our attempt to correlate monomer conversion with chain length extension over time was complicated by the rapid decomposition of the monomer (42% conversion after 27 minutes and 69% conversion after 87 minutes), in contrast to the slower rate of initiation (9% hydrazonium initiated after 27 minutes and 27% hydrazonium initiated after 87 minutes) (Fig. ). As postulated (vide supra), this observation offers a viable explanation for the lower than expected Mn experimental at elevated temperatures. Furthermore, the propagating chain was highly sentitive to hydrolysis, as brief exposure to air (<2 s) prompted termination of the growing polymer. The current work demonstrates that polycyclopropenes can also be accessed with simple hydrazonium initiators, thus demonstrating the ability to access ROMP polymers without metals or irradiation. For cyclopropene monomers, the efficiency of the hydrazonium initiator was comparable to that of traditional ruthenium alkylidenes. We anticipate that the development of more reactive initiators will enable a broader range of monomers and expand the application of this non-metal ROMP platform.