A symmetric, acyclic olefin possessing trithiocarbonate moieties, available in two synthetic steps from commercially available starting materials, is demonstrated to act as a chain transfer agent (CTA) in ring opening metathesis polymerizations (ROMP). The synthetic efficiency of the ruthenium-catalyzed ROMP of 1,5-cyclooctadiene in the presence of this new CTA is investigated as a means of producing telechelic polybutadienes bearing trithiocarbonate endgroups. Telechelic polymers thus synthesized are macromolecular chain transfer agents in the reversible addition fragmentation chain transfer (RAFT) polymerization of styrene and acrylate monomers, enabling the synthesis of ABA-type triblock copolymers of varying compositions possessing monomodal molecular weight distributions.