Condensation polymers form from monomers that each have two functional groups. Every time two monomers join, a small molecule (usually water) is released. Build a polyester or a protein one link at a time and watch the water leave.
The boxes stand for the carbon chain in the middle of each monomer. In the exam you will usually see monomers drawn this way.
| Addition polymerisation | Condensation polymerisation | |
|---|---|---|
| Monomers | Contain a C=C double bond | Each monomer has two functional groups (e.g. –OH, –COOH, –NH₂) |
| Types of monomer | Usually one type | Often two different monomers, or one monomer with two different groups (amino acids) |
| Products | Only the polymer | The polymer and a small molecule, usually water |
| Repeating unit | Same atoms as the monomer | Fewer atoms than the monomers, because water has been lost |
| Examples | Poly(ethene), poly(propene) | Polyesters, polypeptides and proteins |
They start easy and get harder. Write your answer first, then check it.