A variety of thiol nucleophiles was explored using these optimized conditions ( agreement within ~15% in most cases. Incomplete conversion was observed for 4-tertbutylthiophenol and 2-naphthalenethiol under ambient (Table , entries 1 and 3) or inert (N2) atmosphere (Table , entries 2 and 4), which we attribute to the steric bulk of these thiols. Nearly quantitative functionalization was observed for methyl thioglycolate (Table , entries 5 and 6) regardless of atmosphere; however, the SEC peak shape for the product showed distinct broadening and tailing compared to the initial p(TCND-(CO2Me)2), which may be due to possible deleterious side-reactions promoted by the relatively acidic α-protons of the α-mercapto ester (Supporting Information Section 9). By contrast, 1-methyl-3-mercaptoproprionate, a βmercapto ester, underwent high conversion to give a polymer product with no significant change in peak shape (Table , entry 7). Finally, hexanethiol also gave high conversion under these conditions (Table , entry 8). Conclusions. This work represents the first detailed study of the polymerization behavior of TCN and TCND monomers in G3-initiated ROMP. A variety of functional (imides, monoesters, and diesters) TCNs, TCNDs, and exo-NBs were synthesized and their ROMP propagation rates were measured to span a factor of ~13. To understand the relationship between monomer structure and propagation rate, the monomers were featurized using DFT to extract a variety of electronic and steric parameters and search for correlations with measured propagation rate.