Polyolefins catalyst discoveries

Figure 2 The Symyx 1 -octene primary screening workflow from polyolefin catalyst discovery.

Figure 6. Discovery screening workflow for new polyolefin catalysts.

Therefore, the (re)discovery [8] in the last decade of the 20 century of late transition metals as polyolefin catalysts with relatively simple ligands received an im-... 

The next major step, almost two decades after the discovery by ICI of then-high-pressure free radical polymerization of ethylene, was the discovery, from 1951, of (metal oxide and organo-metallic) catalysts that produced essentially linear high molecular weight polyethylene (and other polyolefins) under much lower pressures. These catalyst discoveries occurred almost simultaneously and independently in several laboratories in the USA and Europe [12]. 

The discovery of a highly active family of catalysts based on iron, a metal that had no previous track record in this field, has highlighted the possibilities of further new catalyst discoveries. The search for new catalysts be restricted to metals that have a history of giving polymerization-active centers was no longer needed. The LTMs especially are likely to provide fertile ground for future development, and the greater functional group tolerance of the LTMs also offers the attractive prospect of polar co-monomer incorporation. A relatively small amount of functionality can dramatically transform the adhesion and wettability properties of polyolefins more heavily functionalized products offer the prospect of materials with totally new properties and performance parameters. It is clear that, for olefin polymerization catalysis, the process of catalyst discovery and development is far from over. 

In this contribution, we describe the discovery and application of phenoxy-imine ligated early transition metal complexes (FI catalysts) for olefin polymerization, including the concept behind our catalyst design, the discovery and the polymerization behavior of FI catalysts, and their applications to new polyolefinic materials. 

Transition metal catalysis plays a key role in the polyolefin industry. The discovery by Ziegler and Natta of the coordination polymerization of ethylene, propylene, and other non-polar a-olefins using titanium-based catalysts, revolutionized the industry. These catalysts, along with titanium- and zirconium-based metallocene systems and aluminum cocatalysts, are still the workhorse in the manufacture of commodity polyolefin materials such as polyethylene and polypropylene [3-6],... 

Since their discovery over a decade ago, late transition metal a-diimine polymerization catalysts have offered new opportunities in the development of novel materials. The Ni(II) catalysts are highly active and attractive for industrial polyolefin production, while the Pd(II) catalysts exhibit unparalleled functional group tolerance and a propensity to form unusually branched polymers from simple monomers. Much of the success of these catalysts derives from the properties of the a-diimine ligands, whose steric bulk is necessary to accelerate the insertion process and inhibit chain transfer. 

Also in the 1980s, the discovery of homogeneous stereospecific catalysts for the polymerization of 1-alkenes has opened up new prospects for research on stereospecific polymerization and stereoregular polyolefins. Ewen and coworkers79 achieved this discovery on the basis of earlier research on metallocenes in combination with alkyl-Al-oxanes by Sinn and Kaminsky.10... 

The discovery of a zirconium-based catalyst able to promote polyolefin depolymerization encourages the search for more electrophilic catalytic systems that could be obtained either by changing the metal center or the inorganic support. 

Since the discovery of Ziegler-Natta catalysts, polyolefin industries have been developed mainly by using titanium-based catalysts. However, after the appearance of metallocene catalysts, much emphasis has been placed on those based on zirconium owing to the superiority of their performance over titano-cene catalysts. 

A major breakthrough in polymer production occurred with the discovery of metallocene catalysts [1]. We are now able to make polyolefins with a controlled level of branching (and tacticity). The simplest object is a statistically branched polymer, with a certain overall degree of polymerisation X, and a certain distance (monomer units) between successive branch points, which we shall call b. The basic goal of characterisation is to measure X and b from a minimum number of experiments in dilute solutions. 

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