Addition Polymers
- Polymers are large molecules formed when many small molecules are joined together.
- Addition polymers are formed by addition reaction. The addition reaction joins small molecules without formation of any by-products.
- The small molecules that form polymers are called monomers.
- Alkenes can act as monomers to form polymers.
- Since alkenes are unsaturated, the double bonds in alkenes can break to form new bonds with other monomers.
👇 For example, many ethene monomers join to form poly(ethene). 👇
As you can see, poly(ethene) is basically the repetition of the repeat unit. Since poly(ethene) is a very large molecule, we can just draw the repeat unit to display the formula.
Drawing Repeat Unit of Polymers
When drawing the repeat unit from an alkene monomer,
- Change the double bond into a single bond.
- Add a bond to each end of the repeat unit.
- Add brackets to each end of the repeat unit, and write a n at the lower right end to represent that the repeat unit is repeated many times.
For IGCSE Chemistry, you should be able to draw the repeat unit of poly(ethene), poly(propene), poly(chloroethene) and poly(tetrafluoroethene).
👇Poly(ethene) 👇
👇Poly(propene) 👇
👇 Poly(chloroethene) 👇
👇 Poly(tetrafluoroethene) 👇
Problems in the Disposal of Addition Polymers
Addition polymers are inert and unreactive, so they are non-biodegradable. It means they cannot be biologically decomposed by microorganisms.
Problems associated with the two methods of disposal of addition polymers:
- Landfill (burying in ground) : Burying polymers in the ground fills up land space quickly, and it is hard to find new sites.
- Burning: Burning polymers creates toxic gases, such as carbon dioxide and carbon monoxide.