Ring-opening metathesis polymerization

For other uses of "ROMP", see Romp (disambiguation).

In polymer chemistry, ring-opening metathesis polymerization (ROMP) is a type of chain-growth polymerization involving olefin metathesis.^[1] The reaction is driven by relieving ring strain in cyclic olefins.^[2] A variety of heterogeneous and homogeneous catalysts have been developed for different polymers and mechanisms.^[3] Heterogeneous catalysts are typical in large-scale commercial processes, while homogeneous catalysts are used in finer laboratory chemical syntheses.^[4] Organometallic catalysts used in ROMP usually have transition metal centres, such as tungsten, ruthenium, titanium, etc., with organic ligands.^[5]

Heterogeneous catalysis

ROMP reaction giving polynorbornene. Like most commercial alkene metathesis processes, this reaction does not employ a well-defined molecular catalyst.

Heterogeneous catalysis consists of catalysts and substrates in different physical states. The catalyst is typically in solid phase.^[6] The mechanism of heterogeneous ring-opening metathesis polymerization is still under investigation.^[7]

Ring-opening metathesis polymerization of cyclic olefins has been commercialized since the 1970s.^[4] Examples of polymers produced on an industrial level through ROMP catalysis are Vestenamer, Norsorex and ZEONEX, among others.^[8]

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.^[9]

Frontal ring-opening metathesis polymerization

Frontal ring-opening metathesis polymerization (FROMP) is a variation of ROMP. It is a polymerization system that only reacts on a localized zone.^[10] One example of this system is the FROMP of dicyclopentadiene with a Grubbs' catalyst initiated by heat.^[11]

See also

• Acyclic diene metathesis
• Ring-opening polymerization

Further reading

• Bano, Tahira; Zahoor, Ameer Fawad; Rasool, Nasir; Irfan, Muhammad; Mansha, Asim (June 2022). "Recent trends in Grubbs catalysis toward the synthesis of natural products: a review". Journal of the Iranian Chemical Society. 19 (6): 2131–2170. doi:10.1007/s13738-021-02463-x. ISSN 1735-207X.
• Sveinbjörnsson, Benjamin R.; Weitekamp, Raymond A.; Miyake, Garret M.; Xia, Yan; Atwater, Harry A.; Grubbs, Robert H. (2012-09-04). "Rapid self-assembly of brush block copolymers to photonic crystals". Proceedings of the National Academy of Sciences. 109 (36): 14332–14336. Bibcode:2012PNAS..10914332S. doi:10.1073/pnas.1213055109. PMC 3437898. PMID 22912408.