Addition Polymerisation (SQA National 5 Chemistry): Revision Note

Polymers

• Plastics, like PVC and polythene, are examples of materials called polymers

What are polymers & monomers?

• Polymers are very long-chain molecules

• They are built by linking together a large number of small, repeating molecules called monomers

• The monomers are joined to each other by strong covalent bonds to form the polymer chain

What is addition polymerisation?

• Addition polymerisation is the reaction used to make polymers from unsaturated monomers

  • It is called an addition reaction because the monomer molecules add to each other in a long chain.

• Only monomers with a carbon-to-carbon double bond (C=C), like alkenes, can undergo addition polymerisation.

• During the reaction:

  • The double bond in each monomer breaks open

  • A new single bond forms to link it to the next monomer

  • Only one product is formed

Example: Poly(ethene)

• Many individual ethene monomers react to form one long poly(ethene) chain

Naming addition polymers

• The name of an addition polymer is derived directly from the name of its monomer

  • Simply add the prefix "poly-" to the monomer name

  • Brackets are often placed around the monomer name for clarity.

Examples of naming polymers