Regio- and Stereoselective Ring-Opening Metathesis Polymerization of 3-Substituted Cyclooctenes

3-Substituted <i>cis</i>-cyclooctenes (3<b>R</b>COEs, <b>R</b> = methyl, ethyl, hexyl, and phenyl) were synthesized and polymerized, and the polymers therefrom were hydrogenated to prepare model linear low density polyethylene (LLDPE) samples. The ring-opening metathesis polymerization (ROMP) of the 3<b>R</b>COEs using Grubbs' catalyst proceeded in a regio- and stereoselective manner to afford polyoctenamers [poly(3<b>R</b>COE)] exhibiting remarkably high head-to-tail regioregularity and high <i>trans</i>-stereoregularity. The overall selectivity increases with the increasing size of the <b>R</b> substituent. Hydrogenation of poly(3<b>R</b>COE)s afforded precision LLDPEs with <b>R</b> substituents on every eighth backbone carbon.