Editing Living polymerization (section)

===Living ring-opening metathesis polymerization===
Given the right reaction conditions [[ring-opening metathesis polymerization]] (ROMP) can be rendered living. The first such systems were described by [[Robert H. Grubbs]] in 1986 based on [[norbornene]] and [[Tebbe's reagent]] and in 1978 Grubbs together with [[Richard R. Schrock]] describing living polymerization with a [[tungsten]] carbene complex.<ref>{{cite journal | last1 = Schrock | first1 = R. R. | last2 = Feldman | first2 = J. | last3 = Cannizzo | first3 = L. F. | last4 = Grubbs | first4 = R. H. | year = 1987 | title = Ring-opening polymerization of norbornene by a living tungsten alkylidene complex | journal = [[Macromolecules (journal)|Macromolecules]] | volume = 20 | issue = 5| pages = 1169–1172 | doi = 10.1021/ma00171a053 | bibcode = 1987MaMol..20.1169S }}</ref>

Generally, ROMP reactions involve the conversion of a cyclic olefin with significant ring-strain (>5 kcal/mol), such as cyclobutene, norbornene, cyclopentene, etc., to a polymer that also contains double bonds.  The important thing to note about ring-opening metathesis polymerizations is that the double bond is usually maintained in the backbone, which can allow it to be considered "living" under the right conditions.<ref name=Grubbs>{{cite journal|last=Bielawski|first=Christopher W.|author-link1= Christopher Bielawski |author2=Grubbs, Robert H. |title=Living ring-opening metathesis polymerization|journal=Progress in Polymer Science|date=2007|volume=32|issue=1|pages=1–29|doi=10.1016/j.progpolymsci.2006.08.006}}</ref>

For a ROMP reaction to be considered "living", several guidelines must be met:<ref name=Grubbs />
# Fast and complete initiation of the monomer. This means that the rate at which an initiating agent activates the monomer for polymerization, must happen very quickly.
# How many monomers make up each polymer (the degree of polymerization) must be related linearly to the amount of monomer you started with.
# The [[dispersity]] of the polymer must be < 1.5.  In other words, the distribution of how long your polymer chains are in your reaction must be very low.
With these guidelines in mind, it allows you to create a polymer that is well controlled both in content (what monomer you use) and properties of the polymer (which can be largely attributed to polymer chain length).  It is important to note that living ring-opening polymerizations can be anionic ''or'' cationic.

[[File:Wiki LivingROMP2.png|center|500px|The catalytic cycle of a living ring-opening metathesis polymerization with a metal catalyst.  Note that the ring can be any size, but should contain some significant ring strain on the alkene.]]

Because living polymers have had their termination ability removed, this means that once your monomer has been consumed, the addition of more monomer will result in the polymer chains continuing to grow until all of the additional monomer is consumed.  This will continue until the metal catalyst at the end of the chain is intentionally removed by the addition of a quenching agent.  As a result, it may potentially allow one to create a [[block copolymer|block]] or [[gradient copolymers|gradient copolymer]] fairly easily and accurately.  This can lead to a high ability to tune the properties of the polymer to a desired application (electrical/ionic conduction, etc.)<ref name=Principles>{{cite book|last=Odian|first=George|title=Principles of polymerization|year=2004|publisher=Wiley-Interscience|location=Hoboken, NJ|isbn=978-0471274001|edition=4.}}</ref><ref name=Grubbs />