Olefins syndiotactic copolymers with

It has been discovered that styrene forms a linear alternating copolymer with carbon monoxide using palladium II—phenanthroline complexes. The polymers are syndiotactic and have a crystalline melting point - 280° C (59). Shell Oil Company is commercializing carbon monoxide a-olefin plastics based on this technology (60). 

Similarly, the same catalysts that promote the syndiospecific polymerisation of styrene also polymerise ethylene and a-olefins [106,107], ring-substituted styrenes [6] and conjugated dienes [44,74,108-110], These monomers can also be copolymerised with each other [111-114], Substituted styrenes, which yield syndiotactic polymers by polymerisation run with syndiospecific catalysts, form copolymers with styrene the polymerisation rate increases with increasing nucleophilicity of the comonomer. The random copolymers formed are co-syndiotactic [6,111,112]. 

Styrene and ring-substituted styrenes also form copolymers with carbon monoxide, similarly to ethylene and a-olefins. These styrene/carbon monoxide copolymers are of alternating, highly regioregular head-to-tail structure and are characterised by different stereoregularity (syndiotactic, isotactic) [115-117]. 

Thus, it was not until 1990 that the group of Kaminsky and Arndt-Rosenau took a more detailed look at the homopolymerization of norbornene and the structures of the resulting polymers. Driven by the growing interest in copolymers with high norbornene contents and high glass transition (Tg) temperatures, as well as the unusual properties of PNBs, Arndt-Rosenau et al. used the hydrooligomerization technique to produce saturated model norbornene dimers and trimers with metallocene catalysts known to produce atactic, isotactic, and syndiotactic poly(a-olefins) (1-3, Table 16.1). 

Catalysts that yield highly syndiotactic polypropylene (86% racemic pentads) were also developed. One of them is /-propylene(ri -cyclopentadienyl-r fluorenyl)zirconium dichloride [291]. Initial disclosures of metallocene catalysts were followed by numerous publications in the literature that described similar materials for the polymerizations of either ethylene or propylene, or both, and for formation of various copolymers. Thus, for instance, Kaminsky et al. [292], reported preparaticm of a zirconium dichloride-type catalyst for copolymerization of cyclic olefins with ethylene. These cyclic olefins are cyclopentene, norbomene, and the hindered cyclopentadiene adducts of norbomene [292]. The catalytic system consists of a bridged indene derivative that is combined with methylaluminoxane ... 

Recently we developed catalyst systems, a combination of the Ti complexes having 2,2 -thiobis(4-methyl-6- t-butyl-phenoxy) (TBP) group and MAO, which are specifically active toward styrene, giving syndiotactic polymer and also active toward olefins. In the present work we found that these catalyst systems can copolymerize styrene with ethylene, giving highly alternating ethylene-styrene (ES) copolymer. This paper deals with the results of styrene... 

Metallocenes were developed by Kaminsky and Sinn [42] by developing a new activator. Since then, metallocene technology has progressively undergone changes and has removed the carpet from under ZN catalysts. It is a mature technology now and more than 4 billion dollars has been spent in their development (Table 15). Syndiotactic PP, cyclo-olefin copolymers, and polar monomer incorporation are possible with metallocenes. 

Here, we review (1) research activities in metallocene catalysts, (2) polymerization performances of metallocene catalysts and other single-site catalyst technologies, with examples for polyethylene (PE), cyclo-olefin copolymer (COC), polypropylene (PP), syndiotactic polystyrene (SPS), and cyclo-olefin polymers, and (3) the computational design of metallocene catalysts. 

The relatively open active sites of metallocene catalysts permit the copolymerization of nontraditional cyclic comonomers, snch as styrene and norbomene, with ethylene. Although such resins are not cormnercially available at present, they have the potential for exhibiting novel physical characteristics, possibly expanding the use of polyethylene into new markets. Metallocene technology has also been developed for the production of isotactic and syndiotactic polypropylene, copolymers of propylene with other olefins, and syndiotaetie polystyrene. 

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