Norbomene/ethene

Fig. 20. Dependence of the glass transition temperature of ethene/norbomene copolymers produced by various metallocene/MAO catalysts on the incorporation of norbomene...

Table 23. Properties of a random ethene norbomene copolymer containing 52 mol% of norbomene [105]...

Arndt-Rosenau, M. Beuhch, I. Microstructure of ethene/norbomene copolymers. Macromolecules 1999, 32, 7335-7343. 

Wendt, R. A. Mynott, R. Hauschild, K. Ruchatz, D. Fink, G CNMR studies of ethene-norbomene copolymers. Assignment of sequence distribution using C-enriched monomers and determination of the copolymerization parameters. Macrvmol. Chem. Phys. 1999, 200, 1340-1350. 

The possibility of controlling the interanular wedge angle of ansa-metallocene catalysts and their resulting capability to also enchain olefins, which are otherwise not readily amenable to insertion polymerization, allows the productirMi of copolymers of ethene with cyclic olefins, in particular with norbomene or its substituted derivatives. Based on first observations in this regard [73, 74], ethene/ norbomene copolymers, e.g. with alternating microstmctures [75-77] and with excellent optical and barrier properties, are now commercially produced with ansa-metallocene catalysts by Topas Advanced Polymers (TOPAS ) [78] and by Mitsui Chemical (Apel) [79]. 

Norbomene can be copolymerized with olefins such as ethene and propene. Among these new cyclic olefin copolymers, made accessible from metallocenes [22, 28, 38-93], the ethene-norbomene (E-N) copolymers are the most versatile and interesting ones. 

Hasan, T., Ikeda, T., and Shiono, T. (2004a) Ethene-norbomene copolymer with high nrabomene content produced by nnici-fluorenylamidodimethyltitanium complex using a suitable activator. Macromolecules, 37,8503-8509. 

Kiesewetter, J. and Kamindcy, W. (2003) Ethene/norbomene copolymerization with palladium(II) a-diimine catalysts From ligand screening to discrete catalyst species. Chemistry - A European Journal, 9,1750-1758. 

H) Alternating ethene-norbomene copolymers by group 4 ansa-metallocenes... 

Ethene/propene/diene monomer rubbers (EPDM) are elastomeric terpoly-mers used in the production of sealants, tubing and gaskets and, in the USA, is used in roofing applications. As the name suggests they are prepared by the polymerization of mixtures of ethene, propene and diene monomers, to form cross-links. By far the most common diene used is 5-ethylidene-2-norbomene (ENB). 

One could also imagine a complex that at one site will insert only one certain type of alkene due to high steric constraints (e.g. ethene) and a second alkene at the other site thus giving an alternating copolymer that may even contain stereoregularity, thus obtaining for instance an alternating norbomene/ethene copolymer [34],... 

As said in the introduction there are many more polymers than can be discussed within the limits of this chapter, but we want to add just one example of a group of high-value polymers that is made using the same principles of coordination polymerisation as shown above for the commodity polymers. We mentioned metallocene catalysts that can be used to copolymerise ethene and norbomene to give Topas type products. 

The study of alkene insertions in complexes containing diphosphine ligands turned out to be more complicated than the study of the CO insertion reactions [13], When one attempts to carry out insertion reactions on acetylpalladium complexes decarbonylation takes place. When the reaction is carried out under a pressure of CO the observed rate of alkene insertion depends on the CO pressure due to the competition between CO and ethene coordination. Also, after insertion of the alkene into the acetyl species (3-elimination occurs, except for norbomene or norbomadiene as the alkene. In this instance, as was already reported by Sen [8,27] a syn addition takes place and in this strained skeleton no (3-elimination can take place. Therefore most studies on the alkene insertion and isolation of the intermediates concern the insertion of norbomenes [21,32], The main product observed for norbomene insertion into an acetyl palladium bond is the exo species (see Figure 12.8). 

Further important industrial applications of olefin metathesis include the synthesis of 3,3-dimethyl-l-butene ( neohexene , intermediate for the production of musk perfume) from ethene and 2,4,4-trimethyl-2-pentene, the manufacture of a,co-dienes from ethene and cycloalkenes (reversed RCM), and the ROMP of cyclooctene and norbomene to Vestenamer and Norsorex , respectively. 

The most common alkenes employed in the Pd-catalysed synthesis of alternating polyketones are ethene, styrene, propene and cyclic alkenes such as norbomene and norbornadiene. Even though the mechanism does not vary substantially with the alkene, the reactions of the various co-monomers are here reported and commented on separately, starting with the ethene/CO copolymerisation, which is still the most studied process. As a general scheme, the proposed catalytic cycles are presented first, then the spectroscopic experiments that have allowed one to elucidate each single mechanistic step. 

Monomers are shown in Table 2.1 and in Figure 2.1. The most important monomer is norbornene. Norbornene is in made from di-cyclopentadiene (DCPD) and ethene by a Diels-Alder reaction. 5-Tri-ethoxysilyl-2-norbomene is used for crosslinkable compositions (2). 

They can be handled analogous to thermosetting resins, and thus the use of highly volatile comonomers, such as ethene or prop-ene is prohibitive. Instead, other vinyl monomers are used. A heat curable formulation uses a mixture of tetracyclododecene, 2-norbomene, 5-vinyl-2-norbomene, and divinylbenzene as reactive components (41). The mixture further contains 3,5-di-ferf-butylhy-droxyanisole as antioxidant and a hybrid catalyst system containing a zirconium based metathesis catalyst and a radical catalyst. The metathesis catalyst is benzylidene (l,3-dimesitylimidazolidin-2-yl-idene)(tricyclohexylphosphine)ruthenium dichloride and the radical catalyst is di-ferf-butyl peroxide. 

A route of chemical recycling by pyrolysis has been examined (71). The pyrolysis of COC was performed in a fluidized-bed reactor. Various parameters, such as pyrolysis temperature, fluidizing gas or residence time were varied. Under favorite conditions, the undesired tar fraction could be reduced to a minimum of around 10%. Up to 44% of valuable gases and 45% of aromatic light oils could be obtained at a pyrolysis temperature of 700°C. In general, nor-bornene was recovered only in traces. Thus, it is concluded that 2-norbomene is not sufficiently stable to resist the conditions of pyrolysis. Actually, a retro-Alder reaction occurs resulting in ethene and cyclopentadiene. 

T. Hasan, T. Ikeda, and T. Shiono, Homo- and copolymerization of norbomene derivatives with ethene by ansa-fluorenylamidodimeth-yltitanium activated with methylaluminoxane,. Polym. Sci., Part A Polym. Chem., 45(20) 4581-4587, October 2007. 

I. Tritto, L. Boggioni, and D.R. Ferro, Metallocene catalyzed ethene-and propene co-norbomene polymerization Mechanisms from a de-... 

G.M. Benedikt, E. Elce, B.L. Goodall, H.A. Kalamarides, L.H. McIntosh, L.F. Rhodes, K. Selvy, C. Andes, K. Oyler, and A. Sen, Copolymerization of ethene with norbomene derivatives using neutral nickel catalysts, Macromolecules, 35(24) 8978-8988, November 2002. 

A titanacyclobutane carrier for the living ROMP of norbomene can be converted, by reaction with methanol, into an alkyl titanocene methoxide complex which can then be used in conjunction with EtAlCl2 to propagate the ZNP of ethene, so forming a block copolymer of norbomene and ethene620. 

The INS spectra of ethene [23,24] and propene [24] are discussed in 7.3.2.3 and shown in Fig. 7.16. The spectra are dominated by the effects of molecular recoil. This is less of a problem for propene because it has internal vibrations at lower energy (and hence on low-bandpass spectrometers, lower Q) than ethene. With the much heavier tetrabromoethene [25] this does not occur but the small cross section means that a large (8 g) sample was needed. Tetracyanoethene has been studied by coherent INS [26]. The bicyclic alkene norbomene [27] has been studied by INS because it is the parent compound for a class of advanced composites. 

Dinuclear and trinuclear ferrocenyl derivatives of the type [CpFe(/i-C5H4SiMe2C5H3R R2)ZrCpCl2] (R = R = H R = Me, R = H R = R = Me R = Ph, R = H) and [ CpFe(/r-C5H4SiMe2C5H4) ZrCl2] are very active olefin polymerization catalysts and the former type is active in the copolymerization of ethene and propylene or the terpolymerization of ethylene, propylene and ethylidene-2-norbomene.[ l... 

The use of diazoalkanes instead of 3,3-diphenylcyclopropene provides a series of air-stable alkylidene complexes, Ru(=CHR)(Cl)2(PPh3)2 and Ru(=CHR) (Cl)2(PCy3)2 (R = Me, Et, Ph, p-CgHtCl), which are very efficient catalysts for the ROMP of norbomene and substituted cyclobutenes. Thus, for the Ru(=CHPh)(Cl)2(PPh3)2-initiated ROMP of norbomene, kj/kp = 9 (see Table 11.4). Reaction of Ru(=CHPh)(Cl)2(PCy3)2 with excess ethene gives Ru(==CH2)(Cl)2(PCy3)2, the first methylidene complex which has been isolated and shown to be an active metathesis catalyst (Schwab 1995, 1996). 

---