The first “well-defined” ruthenium catalyst was synthesized by Grubbs in 1992.
The alkylidene source was 3,3-diphenylcyclopropene  (Scheme 3).
Living polymerization with ring opening metathesis is terminated by removing the transition metal from the end of the growing chain and its further deactivation.
Deactivation in this case involves the formation of a complex unable to initiate polymerization .
Ring opening metathesis polymerization (ROMP) is a process of one or more cyclic olefins transformation to polymer catalyzed by metal carbene compounds.
Grubbs Ring Opening Metathesis Mechanism
Indeed, the number of double bonds both in polymer and in monomer is equal [1, 2, 3, 4].
Intermolecular and intramolecular chain transfers are two main side reactions of ROMP (Scheme 2).
During the intermolecular transferring, the active metal-carbene complex located at the end of one macromolecule interacts with the double bond of the adjoined macromolecule, which leads to fragment exchange process.
The reaction proceeds simultaneously in two directions.
One of them provides two polymer chains with the active ruthenium on both.