polymer chemistry Polymer chemistry is a sub-discipline of chemistry that focuses on the structures, chemical synthesis, and chemical and physical properties of polymers and macromolecules. The principles and methods used within polymer chemistry are also applic ...

, ring-opening metathesis polymerization (ROMP) is a type of

chain-growth polymerization Chain-growth polymerization (American English, AE) or chain-growth polymerisation (British English, BE) is a polymerization technique where monomer molecules add onto the active site on a growing polymer chain one at a time. There are a limited n ...

involving olefin metathesis. The reaction is driven by relieving

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 ar ...

in cyclic

olefin In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as α-olefins. The International Union of Pu ...

s. A variety of

heterogeneous Homogeneity and heterogeneity are concepts relating to the uniformity of a substance, process or image. A homogeneous feature is uniform in composition or character (i.e., color, shape, size, weight, height, distribution, texture, language, i ...

and homogeneous catalysts have been developed for different polymers and mechanisms. Heterogeneous catalysts are typical in large-scale commercial processes, while homogeneous catalysts are used in finer laboratory chemical syntheses.

Organometallic Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

catalysts used in ROMP usually have

transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinid ...

centres, such as tungsten, ruthenium, titanium, etc., with organic

ligands In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ...

Heterogeneous catalysis

Heterogeneous catalysis consists of catalysts and substrates in different physical states. The catalyst is typically in solid phase. The mechanism of heterogeneous ring-opening metathesis polymerization is still under investigation. Ring-opening metathesis polymerization of cyclic olefins has been commercialized since the 1970s. Examples of polymers produced on an industrial level through ROMP catalysis are Vestenamer, Norsorex and ZEONEX, among others.

Mechanism

The mechanism of homogeneous ring-opening metathesis polymerization is well-studied. It is similar to any olefin metathesis reaction. Initiation occurs by forming an open coordination site on the catalyst. Propagation happens via a metallacycle intermediate formed after a 2+2 cycloaddition. When using a G3 catalyst, 2+2 cycloaddition is the rate determining step.

Frontal ring-opening metathesis polymerization

Frontal ring-opening metathesis polymerization (FROMP) is a variation of ROMP. It is a polymerization system that reacts via a cascading reaction front after application of a trigger to kick off the reaction in a localized zone. One example of this system is the FROMP of

dicyclopentadiene Dicyclopentadiene, abbreviated DCPD, is a chemical compound with formula . 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 ...

with a Grubbs' catalyst initiated by heat.

References

Polymerization reactions

Heterogeneous catalysis

Mechanism

Frontal ring-opening metathesis polymerization

See also

Further reading

References