Norbornene polymer properties

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. 

Y. Yampol skii, N. B. Bespalova, E. S. Finkel shtein, V. I. Bondar, A. V. Popov, Synthesis, gas permeability, and gas sorption properties of fluorine containing norbornene polymers. Macromolecules, 27, 2872-2878 (1994). 

FIGURE 16.10 Basic concept of Promerus product lines based on copolymers of norbornene derivatives. Different substituents are used to tailor specific polymer properties (R i = alkyl group, oxygen-containing group R2 = trialkylsiloxy group R3 = photosensitive ester group). 

Appear polymers have a similar composition and consist of >90 wt.% of an alkyl norbornene and <10 wt.% of an oxygen-containing norbornene derivative, which is used to increase chain-chain interactions and, thereby, the overall polymer properties. Applications for these polymers are flat panel displays and optical wave guides, both of which are accessible due to the high optical transmission and low birefringence of the polymers, combined with their excellent moisture resistance and ability to be used at high temperature. 

Before discussing the polymerization of monocylic olefins, a brief review of the preparation of polymers from bicyclohep-tenes will acknowledge their historical contribution with respect to polymerization catalysts, polymer structure and properties. Their monomer reactivity in polymerization is much faster than the reactivity of the less strained monocyclic olefins. Anderson (1) and Truett (2) polymerized norbornene... 

Cyclopentene is readily available as a byproduct in the ethylene production. Norbornene 2-ethylhexyl carboxylate is obtained by the Diels-Alder reaction of 2-ethylhexyl acrylate with cyclopenta-diene (5). Norbornene isobornyl carboxylate, norbornene phen-oxyethyl carboxylate, and other related monomers are synthesized according to the same route. Polymers obtained from these esters exhibit excellent properties in terms of controlling the crosslinking density, the associated product modulus, and the glass transition temperature (Tg), thus allowing tailoring the properties of elastomers, plastics and composites. Other suitable monomers are summarized in Table 1.1 and sketched in Figure 1.2. 

Copolymerizations of benzvalene with norbornene have been used to prepare block copolymers that are more stable and more soluble than the polybenzvalene (32). Upon conversion to (CH), some phase separation of nonconverted polynorbomene occurs. Other copolymerizations of acetylene with a variety of monomers and carrier polymers have been employed in the preparation of soluble polyacetylenes. Direct copolymerization of acetylene with other monomers (33—39), and various techniques for grafting p oly acetylene side chains onto solubilized carrier polymers (40—43), have been studied. In most cases, the resulting copolymers exhibit poorer electrical properties as solubility increases. 

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. 

Boamfa et al. investigated macroscopic orientation of disubstituted cyano-biphenyl poly(norbornene) IV-n (n=3,5) using different magnetic fields of up to 20 T. Both the degree of orientation and optical properties were compared with a cyanobiphenyl-substituted acrylate polymer with a spacer of four methylene units [49,50]. 

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... 

In the case of Goodrich poly(norbornene) dielectric polymers [77] (Avatrel) low levels (2-10 mol%) of triefhoxysilylnorbornene (I, Ri = H, R2 = Si(OEt)3) are used to impart good adhesive properties, with the remaining 90+96 of fhe monomer being an alkylnorbornene (I, Ri = H, II,. = alkyl). The alkylnorbornene is selected to tailor the glass transition temperature of the polymer (Section 4.2.3.8) and to impart toughness into fhe product. 

Recent studies in our laboratories have been concerned with the physical properties of sulfonated ionomers such as sulfonate ethylene/propylene/ethylidene norbornene terpolymers (4, or lightly sulfonated polystyrene (S-PS) (11). These ionomers exhibit pronounced ion pair association (at sulfonate levels > 15 milli-equivalents/100 g polymer) to a degree that they appear crosslinked covalently. These interactions can be dissipated by the addition of a polar additive, thereby showing that such associations are indeed physical and do not arise due to covalent crosslinking. 

The living ROMP reactions of norbornene and norbornene derivatives have been used to make a variety of polymers possessing unusual properties. Copolymerization of selected functionalized norbornenes with norbornene has been used to synthesize star polymers and side-chain liquid crystal polymers. " This chemistry has also resulted in the preparation of phase separated block copolymers that contain uniform sized metal or semiconductor nanoparticles. The... 

Scheme 7.36 Synthetic scheme for the polymerization of norbornene and its derivatives via free radical polymerization (FRP), ring-opening metathesis polymerization (ROMP), and vinyl addition polymerization (VAP) techniques. Polymers I, II, and III are isomers that differ in their enchainment and physical properties. Co- and terpolymerization of norbornene and derivatives of norbornene with other alicyclic monomers such as maleic anhydride, methyltetracyclododecene carboxylic acid, etc. are also successfully synthesized with this scheme. (Note that 2, 3- and 2,7-enchainments of repeating units are reported in type I polymers. °°)...

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