Ring-opening metathesis polymerization (ROMP) is a type of

olefin metathesis Olefin metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the scission and regeneration of carbon-carbon double bonds. Because of the relative simplicity of olefin metathesis, it often creat ...

chain-growth polymerization Chain-growth polymerization (American English, AE) or chain-growth polymerisation (British English, BE) is a polymerization technique where Unsaturated compound, unsaturated monomer molecules add onto the active site on a growing polymer chain one ...

. The driving force of the reaction is relief of

ring strain In organic chemistry, ring strain is a type of instability that exists when bonds in a molecule form angles that are abnormal. Strain is most commonly discussed for small rings such as cyclopropanes and cyclobutanes, whose internal angles are ...

in cyclic

olefin In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

s (e.g.

norbornene Norbornene or norbornylene or norcamphene is a highly strained bridged cyclic hydrocarbon. It is a white solid with a pungent sour odor. The molecule consists of a cyclohexene ring with a methylene bridge between carbons 1 and 4. The molecule carr ...

or cyclopentene). A variety of

heterogeneous Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, size ...

and

homogeneous catalyst In chemistry, homogeneous catalysis is catalysis by a soluble catalyst in a solution. Homogeneous catalysis refers to reactions where the catalyst is in the same phase as the reactants, principally in solution. In contrast, heterogeneous catalysis ...

s have been developed. Most large-scale commercial processes rely on the former while some fine chemical syntheses rely on the homogeneous catalysts.

Catalysts Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

are based on transition metals such as W, Mo, Re, Ru, and Ti.

Heterogeneous catalysis and applications

Ring-opening metathesis polymerization of cycloalkenes has been commercialized since the 1970s. Examples of polymers produced on an industrial level through ROMP catalysis are Vestenamer or trans-polyoctenamer, which is the metathetical polymer of cyclooctene. Norsorex or polynorbornene is another important ROMP product on the market. Telene and Metton are polydicyclopentadiene products produced in a side reaction of the polymerization of norbornene. The ROMP process is useful because a regular polymer with a regular amount of double bonds is formed. The resulting product can be subjected to partial or total hydrogenation, or can be functionalized into more complex compounds.

Homogeneous catalysts

The most common

for ROMP is also the best understood. In particular, the third generation Grubbs' catalyst (known as G3) has excellent

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...

tolerance, air-stability, and fast

initiation Initiation is a rite of passage marking entrance or acceptance into a group or society. It could also be a formal admission to adulthood in a community or one of its formal components. In an extended sense, it can also signify a transformation ...

and

propagation Propagation can refer to: *Chain propagation in a chemical reaction mechanism *Crack propagation, the growth of a crack during the fracture of materials *Propaganda, non-objective information used to further an agenda *Reproduction, and other forms ...

rates. The fast initiation rates of G3 results in a

living polymerization In polymer chemistry, living polymerization is a form of chain growth polymerization where the ability of a growing polymer chain to terminate has been removed. This can be accomplished in a variety of ways. Chain termination and chain transfe ...

with a narrow polymer molecular weight dispersion. This has made ROMP a popular choice for making advanced polymer architectures and functional polymer products. It is common to quench these reactions with ethyl vinyl ether to generate the free polymer chain and an inactive Ru Fischer carbene complex.

Mechanism

The mechanism of ROMP is similar to any

reaction.

Initiation Initiation is a rite of passage marking entrance or acceptance into a group or society. It could also be a formal admission to adulthood in a community or one of its formal components. In an extended sense, it can also signify a transformation ...

occurs by formation of an open coordination site. Propagation occurs via a metallacyclobutane intermediate.

Frontal ring-opening metathesis polymerization

Frontal ring-opening metathesis polymerization (FROMP) is a variation of ROMP in which it is a latent polymerization system that react fast, only upon ignition. One example of this system is the FROMP of

dicyclopentadiene Dicyclopentadiene, abbreviated DCPD, is a chemical compound with formula C10H12. At room temperature, it is a white brittle wax, although lower purity samples can be straw coloured liquids. The pure material smells somewhat of soy wax or camphor ...

with a Grubbs' catalyst initiated by heat.

References

{{DEFAULTSORT:Ring Opening Metathesis Polymerization Polymerization reactions

Heterogeneous catalysis and applications

Homogeneous catalysts

Mechanism

Frontal ring-opening metathesis polymerization

See also

References