Tuesday, May 17, 2011

Karl Ziegler: "Consequences and Development of an Invention"

Karl Ziegler, German chemist (1898-1973)

Karl Ziegler, then director of the Max-Planck-Institute-for Coal Research, describing what he and co-workers discovered ten years prior to winning the 1963 Nobel Prize in Chemistry:
The catalyst is prepared simply by simultaneously pouring, with exclusion of air, two liquid materials into about two liters of a gasoline-like hydrocarbon, after which ethylene is introduced, while stirring. The gas is absorbed quickly; within an hour one can easily introduce 300-400 liters of ethylene into the two liters of liquid. At the same time, a solid substance precipitates, and can scarcely be stirred anymore. If the brown catalyst* is then destroyed, by the addition of some alcohol and by the introduction of air, the precipitate becomes snow-white and can be filtered off. In its final state it will accumulate in amounts of 300-500 g, as a dry, white powder.
~Karl Ziegler "Consequences and development of an invention"
*The two co-catalysts were titanium and aluminum chlorides

Polyethylene had been known earlier. A British company, ICI, held patents for what they called "polythene" (hmm, maybe related to the Beatles' "plasticene"?), but ICI's polyethylene was different animal than Ziegler's polyethylene. The difference is at the atomic level. Though both plastics were polymers of ethylene, the older, inferior product was highly branched:
Ziegler's new process for making polyethylene essentially made perfectly linear chains of polymer with very little branching. The bulk properties of the two were markedly different. The density differences are akin to what one expects from trying to pack together a bunch of branches versus bunches of straight sticks.

Ziegler and his Institute became independently wealthy as the plastic age began in earnest.

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