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Ethylene as a Monomer

 
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Students learn to identify that ethylene serves as a monomer from which polymers are made

"I am inclined to think that the development of polymerisation is perhaps the biggest thing chemistry has done, where it has had the biggest effect on everyday life"
- Lord Todd, Chemical and Engineering News, 58, 29 (1980)
quoted in "History of Polyolefins: the world's most widely used polymers", R. B. Seymour and T. Cheng, editors.

So what is poly(ethylene) (also known as poly(ethene)), where does it come from, and why is it the most useful and interesting thing in the universe (with the exception of poly(styrene), of course)?

There is one class of reaction that ethylene can undertake that is particularly useful (it keeps us polymer scientists in a job, at least).

Addition Polymerisation

The most widespread use of ethylene (and most important, as far as we are concerned) is in polymerisation. The addition polymerisation reaction that ethlyene can undergo is described in brief by the following reaction.


Ethene can undergo an addition polymerisation reaction to form poly(ethylene).

Poly(ethylene) is probably the most important synthetic polymer of them all. There are a number of different forms prepared by different methods. The exact details of how poly(ethylene) is made will be discussed a bit later in our wander through the world of polymers.

More ethylene is used to make poly(ethene) than any other application. Poly(ethene) can be found in many different forms You may have noticed that plastic kitchen film is very different from the relatively hard plastic used in plastic juice bottles, and the extremely hard plastic used in bulletprood vests... This is because all polyethene is not created equal.