Ethylene/norbornene

Figure 14 Crystallinity of ethylene/norbornene copolymers. (From Ref. 25. Reprinted with permission from Elsevier Science.)...

Development of a reduced-order model for metallocene-catalyzed ethylene-norbornene copolymerization reaction... 

These catalysts were used in combination with methylaluminoxane (MAO) for ethylene-norbornene co-polymerization and compared with isopropylidene[9-fluorenylcyclopentadienyl]zirconium dichloride catalyst activity under identical conditions. 

Note phr = parts per hundred parts of rubber, ENB = ethylene norbornene (curing site in the elastomer), TMPT = trimethylolpropane trimethacrylate (prorads). 

The alternating copolymers are characterized both by a glass transition temperature (130°C for ethylene/norbornene copolymers) and a melting point (295°C for the totally alternating copolymer). The melting point and the crystallinity of these copolymers may be influenced by choice of the metallocene and the conditions of polymerization. Compared with the statistical copolymers, the alternating structures show better resistance to nonpolar... 

Fig. 28. Dependence of the glass transition temperature of ethylene/norbornene copolymers produced by various metallocene/MAO catalysts on the incorporation of norbornene (24).

The cyclocarbonylation of a,/ -unsaturated imines 54 also gave five-membered lactams 55 or 56 with or without 57 depending on the substitution patterns of the starting materials (Eq. 26) [40]. Such a useful [4+1] cycloaddition was applied to a cyclic imine 58 conjugated with a cyclohexenyl group to afford an interesting aza-tricycle 59 in 65% yield (Eq. 27). In the presence of an alkene such as ethylene, norbornene, and vinyltrimethylsilane, a similar cyclocarbonylation of a,/l-unsaturated imines 60 gave rise to a-alkylated /5,y-unsaturated lactam 61 in various yields (Eq. 28) [41,42]. Several plausible mechanisms are proposed for the formation of 61, but the elucidation of the entire mechanism calls for further work. 

Single-site metallocene catalysts are also highly reactive vis-a-vis cycloolefins such as cyclobutene, cyclopentene or norbornene. While homopolymers of these cycloolefins have melting temperatures (>380°C), much too high for technical processability, ethylene-cycloolefin copolymers (COC s) - e.g. ethylene-norbornene copolymers - are amorphous materials with glass transition temperatures, above which they become soft and processable [W. Kaminsky, J. Polym. Sci. A, Polym. Chem., 2004, 42, 3911]. 

Ethylene-norbornene copolymers, which have thermoplastic properties when heated above their glass transition temperatures of ca. 200-250°C, have been commercialized by Ticona GmbH under the trade name TOPAS (Tliermoplas-tic Olefin Polymer of Amorphous Structure). Their properties - exceptional transparency, low double refraction, high stiffnes and hardness, low permeability for moisture and excellent biocompatibility - make these ethylene-norbornene copolymers particularly valuable as engineering polymers, for optical applications and as materials for food and medical packaging. 

Figure 25 Alternative concatenation microstructures in ethylene-norbornene copolymers.

ButG5H3, G9H6) have been synthesized either by the standard salt metathesis or the amine elimination procedure. These compounds are used as pre-catalysts for norbornene homopolymerization and ethylene-norbornene co-poly-merization. The influence of the catalyst symmetry and structure on the activity, norbornene incorporation, and polymer and co-polymer microstructure has been studied.706... 

Within the family of cycloolefin co-polymers, the most important from a material properties standpoint, are the ethylene/norbornene co-polymers. These co-polymers, dubbed COC for cycloolefin co-polymers, are produced by Ticona and Mitsui under the tradenames Topas and Apel , respectively. An overview of properties and applications (for example, blisters for pills) can be found on Ticona s Topas homepage.607 Detailed ethylene/norbornene copolymerization studies with different 4/-symmetric and ansa-Cp-amido catalysts, with listing of co-polymerization parameters, have been published.608 611 NB is inserted exclusively in the cis-2,3-exo-modc (Scheme 25), and most of the metallocene catalysts tend to produce alternating co-polymers,609 612 due to the low reactivity of the M-NB intermediate toward further NB insertion. This mode of NB insertion prevents f3-H transfer, and thus ethylene/ norbornene co-polymers have increasing molecular masses at increasing NB content.611... 

The correlation between composition and glass transition temperature in ethylene/norbornene co-polymers is shown in Figure 22. 

Syndiotactic propylene/1-octene co-polymers have been prepared.866 In propylene/norbornene co-polymerization, catalyst activity strongly decreases with the increase of norbornene in the feed. Very high Tg co-polymers have been produced at high norbornene incorporation. Surprisingly, Tg differences with the ethylene/norbornene co-polymers are small (Figure 36). 

Figure 36 Correlation between norbornene content and glass transition temperature in ethylene/norbornene (O)621 and propylene/norbornene ( ) co-polymers.861,862 The best linear fit for the propylene/norbornene data extrapolating at Ts = 330 °C for polynorbornene is also shown.

Finally, ethylene/norbornene co-polymerization with the dicarbollide Ti and Zr complexes has been also reported.1238... 

The last observations automatically lead to the conclusion that non-activated alkenes also could undergo these reactions. Indeed it was found that ethylene, norbornene, norbomadiene198) and allene 199) react with methylenecyclopropane to give cycloadducts (Scheme 7). The reason for the limitation to these alkenes lies in the ability of methylenecyclopropane to compete successfully with alkenes in it-complexation to the metal. Thus cyclodimerization of methylenecyclopropane is much faster than codimerization with other alkenes, which give less stable ic-com-plexes with Pd(0). 

Finally, the ethylene/norbornene copolymers obtained using the nickel catalysts are essentially indistinguishable from those obtained using metaUocene-based early transition metal catalysts, both in terms of the microstructure and such physical properties as Tg and tensile modulus. For the ethylene/norbornene polymers synthesized, the glass transition temperature (Tg) increases smoothly with increasing norbornene content. 

Ethylene-norbornene 16 1,2-Diimines Pd Conventional b Catalyst performance 2003 44... 

This case has been recently described in the literature and is represented by the highly disordered crystalline form of alternated ethylene-norbornene (EN) copolymers [121]. The crystallinity of EN copolymers will be discussed in a following section, pointing out at the structural analogies with the conventional plastic crystals. 

Fig. 18 X-ray powder diffraction profiles of ethylene-norbornene copolymer samples with norbornene content close to 50% (A)-(C), and solid norbornane in f.c.c. polymorph stable a T>30.6°C, (D) redrawn from [121]. Sample (A) is a random copolymer and amorphous. Samples (B) and (C) have a prevailing alternating constitution and are both crystalline. Sample (C) is essentially atactic, whereas sample (B) has a prevailing diisotactic configuration. (Reprinted with permission from [121]. Copyright 2003 by the American Chemical Society)...

Recently, it has been shown that alternating ethylene-norbornene (EN) copolymers are crystalline [202-206] and that this crystallinity is not necessarily related to a regular succession of configurations of stereoisomeric centers in the norbornene units [121,207]. 

Fig. 20 (A,B) Meso- and (C,D) racemo- norbornene-ethylene-norbornene (N-E-N) sequences, in the lowest energy conformation. R and S indicate the configuration of the chiral carbon atoms of the norbornene units. Depending on the succession of the configurations R and S the meso diads may assume Z- or S-shapes (A,B)> whereas the racemic diads may assume a C shape with different orientation (C,D). (Reprinted with permission from [121], Copyright 2003 by the American Chemical Society)...

CYCLIC OLEFIN POLYMERS. See Ethylene-Norbornene Copolymers. 

Cyclic olefin monomers are derivatives of CPD or DCPD. Norbomene derivatives are produced by the Diels-Alder condensation of an olefin and CPD. For instance, 2-norbornene (9) is obtained by reacting excess ethylene with DCPD at a high temperature (>200°C) and pressure (>2900 psia), the condition in which the DCPD is cracked to CPD (64). Reactions of CPD or DCPD at high temperatures with styrene and norbomene yield, respectively, the phenylnorbomene (10) and tetracyclododecene (11) (see Ethylene-Norbornene Copolymers). 

More About Engineering Thermoplastics. Many of the individual resins mentioned in this overview are covered in articles devoted to them. Cross references are provided in Table 1. A list of related articles is as follows Acetal Resins Acrylic Ester Polymers Acrylonitrile and Acrylonitrile Polymers (SAN and ABS) Ethylene-Norbornene Copolymers Liquid Crystalline Polymers, Main-Chain Methacrylic Ester Polymers ... 

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