Polyethylene oligomers (PEOlig) can be used as cosolvents and sometimes soluble catalyst supports in ring-opening metathesis polymerization (ROMP) reactions. As a catalyst support, this polyolefin serves as an N-heterocydic carbene ligand for a ROMP catalyst, making it soluble at 70 degrees C and insoluble at room temperature. As a cosolvent, unfunctionalized PE oligomers facilitate quantitative separation of PEOlig-bound Ru-catalyst residues from polymer products. In these cases, the insolubility of the unfunctionalized polyethylene (Polywax) and its entrapment of the PEOlig-supported Ru residue in the product phase at room temperature afford ROMP products with Ru contamination lower than other procedures that use soluble catalysts. These separations require only physical processes to separate the product and catalyst residues-no additional solvents are necessary. Control experiments suggest that most (ca. 90%) of the Ru leaching that is seen results from Ru byproducts formed in the vinyl ether quenching step and not from the polymerization processes involving the PEOlig-supported Ru complex.