Addition Polymerisation (WJEC GCSE Chemistry: Combined Science)

What is addition polymerisation?

• Addition polymerisation involves small, reactive molecules called monomers reacting together to form a polymer
  • A monomer is a compound which contains a carbon-carbon double bond / C=C
• The reactivity of a monomer is due to its carbon-carbon double bond / C=C
• One of the bonds in each carbon-carbon double bond / C=C breaks open
  • This allows the molecule to join to another adjacent molecule
  • The end result is a polymer that contains only single bonds 
• Addition polymerisation of different alkene monomers forms various polymers including:
  • Polythene
  • Poly(propene)
  • Poly(vinylchloride)
  • Poly(tetrafluoroethylene) 
• To name a polymer, put the name of the monomer in brackets and add poly- as the prefix
  • The only exception to this is poly(ethene), which becomes polythene

Writing equations for addition polymerisation

• The equations used to represent the addition polymerisation of any monomer use structural formulae 
  • This is to show what happens to the bonds inside the monomer
• Addition polymerisation equations all follow a similar pattern:
  1. Draw the reactant monomer, with a lower case n in front to show that there are "some" monomers involved
  2. Draw the same molecule as a product but with a carbon-carbon single bond
  3. Add brackets around the product molecule
  4. Add one single bond to each carbon atom, continuing outside of the brackets
     • These are often called continuation bonds
  5. Add the lower case n after the brackets 

Addition polymerisation of different monomers

In all examples, the C=C bond breaks open and attaches to an adjacent molecule