Metallocene-based polymers

The 50th Anniversary of Metallocene-Based Polymers, a special issue of./. Inorg. Organometal. Polym. Mater., 15(1), 1-196 (2005). 

The first example of a metallocene-based polymer, polyvinylferrocene, was described in 1955. This macromolecule was synthesized via the radical and cationic... 

In the USA Exxon Chemical and Dow Plastics were the leaders in the metallocene technology. While Exxon explored both mono- and bis-cyclopentadienyl metallocenes, Dow focused on constrained geometry catalysts based on Ti-monocyclopentadienyl metallocenes. Exxon first produced metallocene-based polymers with its Exxpol catalysts in 1991. Dow uses its INSITE technology to make ethylene-octene copolymers, introduced in 1993. Copolymers with up to 20 wt% octene are sold as AFFINITY plastomers, competing with specialty polymers in packaging, medical devices, and other applications. Dow, producing its own catalyst, considers that it leads to the uniform introduction of comonomers and long-chain branches that improve processability of otherwise linear polymers. 

While the range of the new metallocene-based polymers includes such specialty polymers as cyclo-olelin copolymers (COC), syndiotactic polystyrene, ethylene/ styrene copolymers, which are stiU in the developmental stage, commercially, the most prominent candidates are the elhylene/a-olefin copolymers such as ethylene/ butylene or hexene copolymers (Exxon s Exact ) or ethylene/l-octene copolymers (Dow s Engage and Affinity ). Depending on the comonomer content, these copolymers have been classified as plastomers or elastomers. At comonomer levels of >25 %, the copolymers exhibit the characteristics of thermoplastic elastomers such as high softness, toughness, flexibility, and resilience and hence been referred to as polyolefin elastomers (POE). CompositionaUy, these POEs usually contain 65 % ethylene and 35 % octene-1, hexene-1, or butene-1 as comonomers. 

Thomas KR, lonescu A, Gwyther J, Manners I, Barnes CHW, Steiner U, Sivaniah E (2011) Magnetic properties of ceramics from the pyrolysis of metallocene-based polymers doped with palladum. J Appl Phys 109 073904... 

Reinking and co-workers have raised the possibility that at least some of the LCB seen in metallocene-based polymers may arise from an unusual aliphatic C—H activation of dissociated ( dead ) polymer molecules (eq. 25) (As part of a study of non-metallocene vanadium catalysts, see Ref 164). In this study, abridged bis(indenyl) zirconocene was found to incorporate ethylene units into the heptane solvent, while an unbridged version, (n-C4H9Cp)2ZrCl2, did not. 

J. Scheirs and W. Kaminsky, Metallocene-Based Polymers, Vols. 1 and 2, Wiley, Chichester, England, 2000. 

Metallocene/MAO and other single-site catalysts allow the synthesis of tailored polyolefin structures in a way that was impossible in previous years. The known dependence of the kind of metallocene-based polymer on the catalyst structure allows the modeling of the reaction kinetics and the polymerization process... 

Since the first example of a metallocene based polymer was reported in 1955 by Arimoto and Haven, just a few years after the discovery of ferrocene, there has been an ever increasing interest in the development of oiganometallic polymers. This... 

The core for the production of metallocene-based polymers is the Novolen Gas Phase Process [64] which combines metallocene drop-in technology (Fig. 40). The core of the process is one or two vertical stirred reactors in series. The process can manufacture... 

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