Ring-Opening Metathesis Polymerization ROMP

During the last years ROMP has been developed to generate self-healing polymers. In these polymers droplets of dicyclopentadiene and of Grubbs-catalyst are incorporated. When the polymer cracks the droplets burst open, the catalyst comes into contact with the monomer and the plastic ideally heals itself [111]. This methodology is still far from application but it does indicate the power of ROMP. 

Recently, while investigating the polymerization behavior of catalyst 10, it was found that this catalyst is quite effective at forming polymers with high 

The thiolate catalysts 4 and 26, developed by the Hoveyda group, also display remarkable selectivities for Z olefins in the ROMP of norbornene and COD, with 

Grubbs, R.H. (2003) Handbook of Metathesis, Wiley-VCH Verlag GmbH, Weinheim. 

and Sandberg, R.J. (2007) Advanced Organic Chemistry, Part A Structure and Mechanisms, 2nd edn. Springer, New York. 

Jensen, V.R., Occhipinti, G, and Hansen, F.R, (2011) Novel olefin metathesis catalysts. International Publication Number WO 2012/032131 Al, Sept. 8, 2011, 

Inter- (A) and intramolecular (B) chain transfer reactions in ROMP. 

The extent of this process strongly depends on temperature, monomer concentration, cisitrans configuration of the double bonds within the polymer backbone, solvent, reaction time and, probably most important, on the steric bulk of the monomer used. 

Tremendous efforts have been put into the development of weU-defined singlesite transition metal alkylidenes. Mainly the work of R.H. Gmbbs and R.R. Schrock (awarded with the Chemistiy Nobel Prize 2005, shared with Y. Chauvin) led to the development of weU-defined transition metal alkylidenes that rapidly outrivaled the traditional initiator systems. These initiators have the advantage of being well-defined compounds and in particular of possessing preformed metal-alky lidenes. 

The types of monomer susceptible to metathesis polymerization reactions are limited, however, and those that are most suitable are strained ring structures. Thermodynamic considraations account for the lack of reaction with six-membraed rings, and strain-free cyclohexene derivatives or conjngated cyclodienes tend to be excluded. Newer catalysts that can polymerize polar monomers are now available. Cyclic monomers contain fnnctional groups, -OH, -COOH, -COOR, -CONHj, and -NHj, can be used with the newer catalysts that have been developed. 

One of the first applications envisioned of ROMP was the preparation of polyenes with rubber-like properties by ROMP of cyclopentene. Although this polymer did not have the optimum product profile, the polymer obtained by ROMP of cyclooctene can indeed be used in blends with other rubbers, conferring on the final product improved mechanical properties and simplifying its processing. This polymer, called Vestenamer 8012, is being produced by Chemische Werke Hiils, Marl, Germany, and the annual capacity in 1990 reached 12000t. 

As for other types of polymerization, ROMP can only be initiated if the concentration of monomer reaches a certain value and the temperature does not exceed a given limiting value. Hence, polymerization occurs more readily at high 

With the discovery of ruthenium carbene complexes, which can catalyze ROMP in the presence of air and water [584,820], ROMP could be extended to hydrophilic 

Telechelic end-group-functionalized PNB polymers with H bonds on only one end have been generated by Week et al. (Ambade et al., 2009) relying on the quantitative and fast reaction of ethyl-vinyl ethers with the growing ruthenium-carbene on the chain end. Thus, the living polymer (37) can be directly reacted with ethyl-vinyl ethers containing the respective H bond resulting in the quantitative attachment to yield the fully functionalized polymer (38). A major drawback of this method, however, is the tedious synthetic approach to the respective substituted ethyl-vinyl-ethers, which require a multistep procedure. 

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Aqueous ring-opening metathesis polymerization (ROMP) was first described in 1989 (90) and it has been appHed to maleic anhydride (91). Furan [110-00-9] reacts in a Diels-Alder reaction with maleic anhydride to give exo-7-oxabicyclo[2.2.1]hept-5-ene-2,3—dicarboxylate anhydride [6118-51 -0] (24). The condensed product is treated with a soluble mthenium(Ill) [7440-18-8] catalyst in water to give upon acidification the polymer (25). Several apphcations for this new copolymer have been suggested (91). 

Ring-Opening Metathesis Polymerization. Several new titanacyclobutanes have been shown to initiate living ring-opening metathesis polymerization (ROMP) systems. These have been used to make diblock and triblock copolymers of norbomene [498-66-8] (N) and its derivatives (eg, dicyclopentadiene [77-73-6] (D)) (Fig. 2) (41). 

A drawback to the Durham method for the synthesis of polyacetylene is the necessity of elimination of a relatively large molecule during conversion. This can be overcome by the inclusion of strained rings into the precursor polymer stmcture. This technique was developed in the investigation of the ring-opening metathesis polymerization (ROMP) of benzvalene as shown in equation 3 (31). 

Ring-opening metathesis polymerization (ROMP) of 1,4-cyelooctadiene was used to prepare poly(l,4-B) terminated with halo end groups.647 This was then used as a macroinitiator of ATRP with heterogeneous Cu bpy catalysts to form PS- >/ti /r-poly(l,4-B)-WoeA -PS and PMMA-Moc.T-poly(l,4-B)-Wof A-PMMA. 

Scheme 2 Different modes of the olefin metathesis reaction cross metathesis (CM), ringclosing metathesis (RCM), ring-opening metathesis (ROM), acyclic diene metathesis polymerization (ADMET), and ring-opening metathesis polymerization (ROMP)...

ROMP. See Ring-opening metathesis polymerization (ROMP)... 

The polynorbornenes X bearing cyclotriphosphazenes with -0(CH2CH20)x-CH3 (x=l, 2,3,7.2) side groups have been prepared via ring opening metathesis polymerization (ROMP) and complexed with LiS03Cp3 and LiN(S02Cp3)2 (10-60% molar ratios) by Allcock [619,620]. 

Wolfe and Wagener have developed main-chain boronate polymers (59) (Fig. 38) by the acyclic diene metathesis (ADMET) polymerization of symmetrical ,oj-dienes, containing both methyl- and phenyl-substituted boronate functionalities using Mo and Ru catalysts.84 The ring-opening metathesis polymerization (ROMP) of several norbornene monomers containing methyl- and phenyl-substituted boronates into... 

Polymeric isoxazolines were prepared by cycloaddition of nitrile oxides to norbomadiene followed by ring-opening metathesis polymerization (ROMP) <06PLM3292 06MM3147>. 

In the case of other Group 6 metals, the polymerization of olefins has attracted little attention. Some molybdenum(VI) and tungsten(VI) complexes containing bulky imido- and alkoxo-ligands have been mainly used for metathesis reactions and the ring-opening metathesis polymerization (ROMP) of norbornene or related olefins [266-268]. Tris(butadiene) complexes of molybdenum ) and tungsten(O) are air-stable and sublimable above 100°C [269,270]. At elevated temperature, they showed catalytic activity for the polymerization of ethylene [271]. 

Ring-Opening Metathesis Polymerization (ROMP) and other Ring-Opening Reactions... 

Fig.4A,B. Ring-opening metathesis polymerization (ROMP) A Structures of organometal-lic initiators that have been used in ROMP to generate neobiopolymers. B General pathway for polymer synthesis using ROMP. Molybdenum-initiated reactions are typically capped with aldehydes and ruthenium-initiated with end ethers.

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