Compare addition polymerisation and condensation polymerisation. Include in your answer the type of monomer required for each and what is produced alongside the polymer in condensation polymerisation.

Addition polymerisation uses monomers that contain a carbon–carbon double bond (unsaturated monomers, e.g. alkenes). The reaction proceeds with the double bond opening and the monomers linking together, producing only the polymer.

Condensation polymerisation uses monomers that have two different functional groups. During the reaction these groups react to form covalent bonds, and a small molecule such as water (or methanol, HCl, etc.) is released as a by‑product.

Thus, addition polymerisation requires unsaturated monomers and gives only the polymer, whereas condensation polymerisation requires bifunctional monomers and produces a small molecule alongside the polymer.