Polymers
Polymers are long chain molecules that occur naturally in living things and can also be made by chemical processes in industry. Plastics are polymers, so polymers can be extremely useful.
Repeating units
Polymer molecules are very large compared with most other molecules, so the idea of a repeat unit is used when drawing a displayed formula. When drawing one, you need to:
- change the double bond in the monomer to a single bond in the repeat unit
- add a bond to each end of the repeat unit
It can be tricky to draw the repeat unit of poly(propene). Propene is usually drawn like this:
It is easier to construct the repeat unit for poly(propene) if you redraw the monomer like this:
You can then see how to convert this into the repeat unit.