Addition polymerisation: monomers joining into a polymer chain (PE, PP, PVC, PTFE, PS)

ChemistryBiomolecules & PolymersAges 17–18

Monomer molecules with a C=C double bond (ethylene, propylene, vinyl chloride, tetrafluoroethylene, styrene) move freely; as polymerisation runs, the π bond opens and each monomer joins the growing end of the chain. Students count the number of repeat units n, see the equation n CH₂=CHX → (–CH₂–CHX–)n, the polymer's molar mass M = n × M(monomer), and the matching polymer name; a monomer can also be tapped to join it in by hand.