Addition polymerisation — common mistakes

When asked to draw a 'repeat unit', you must use square brackets. Crucially, the single bonds forming the main polymer chain must extend through the brackets to show that the chain is continuous. Forgetting these bonds is a common way to lose a mark.

It is called addition polymerisation because the monomer molecules add to one another in such a way that the polymer is the only product. No atoms or small molecules are lost or eliminated during the reaction.

The 'n' is called the degree of polymerisation. It represents the number of repeating monomer units in the polymer chain, which is typically a very large integer, often in the thousands or tens of thousands.

No, alkanes cannot undergo addition polymerisation. They are saturated molecules, meaning they only have single C-C bonds. The key requirement for a monomer in addition polymerisation is the presence of a C=C double bond that can break and form new bonds to link the units together.