Question

Why is ethylene used as monomer?

Answer 1

Because (i) it is cheap; you get it from a hole in a ground; and (ii) processes exist to transform the monomer into a higher value polymer.

Explanation:

As you know, it is relatively hard to make a `C-C` bond. Polyethylenes feature 100's of `C-C` bonds in a linear chain. This material is a higher value commodity, and its synthesis from ethylene is cheap and straightforward by means of transition metal catalysis.

One of ethylene surprising uses is as a plant hormone. By means of ethylene gas you can stimulate the ripening of unripe fruit (a good strategy when you have a warehouse full of green tomatoes or green bananas). In these circumstances, small quantities of ethylene are generated by electrolytic reduction of ethyl alchohol.