Addition and Condensation Polymerisation — AQA GCSE Chemistry (Separate)
Polymers are made by joining many small monomers. There are two types of polymerisation.
Addition polymerisation
In addition polymerisation, many alkene monomers (with C=C double bonds) join together to form a polymer — the only product.
- The double bond opens up and the monomers link into a long chain.
- The repeating unit has the same atoms as the monomer.
- Example: many ethene molecules → poly(ethene).
Because there is only one product and the repeating unit matches the monomer, you can draw the polymer from the monomer (and vice versa).
Condensation polymerisation (Higher Tier)
In condensation polymerisation, monomers join and a small molecule (usually water) is released each time a bond forms.
- It usually involves two different monomers, each with two functional groups (e.g. diols and dicarboxylic acids forming polyesters).
- Two products: the polymer and the small molecule (e.g. water).
Comparing the two
| Addition | Condensation | |
|---|---|---|
| Monomers | one type (alkenes, C=C) | usually two types, two functional groups |
| Products | polymer only | polymer + small molecule (water) |
Exam tips
- Addition polymerisation: alkene monomers, C=C opens, polymer is the only product.
- Draw the repeating unit from the monomer (keep the same atoms).
- Condensation polymerisation releases a small molecule (water) and uses monomers with two functional groups.
- Know the differences between the two types.