AQA GCSE Chemistry

Revision Notes

7.3.1 Addition Polymerisation

Polymerisation

  • Polymers are large molecules of high relative molecular mass and are made by linking together large numbers of smaller molecules called monomers
  • Each monomer is a repeat unit and is connected to the adjacent units via covalent bonds
  • Polymerisation reactions usually require high pressures and the use of a catalyst
  • Many everyday materials such as resins, plastics, polystyrene cups, nylon etc. are polymers
  • These are manufactured and are called synthetic polymers
  • Nature also produces polymers which are called natural or biological polymers

Polymers - Basic, IGCSE & GCSE Chemistry revision notes

Diagram showing how lots of monomers bond together to form a polymer

Representing Polymers

  • Addition polymers are formed by the joining up of many monomers and only occurs in monomers that contain C=C bonds
  • One of the bonds in each C=C bond breaks and forms a bond with the adjacent monomer with the polymer being formed containing single bonds only
  • Many polymers can be made by the addition of alkene monomers
  • Others are made from alkene monomers with different atoms attached to the monomer such as chlorine or a hydroxyl group
  • The name of the polymer is deduced by putting the name of the monomer in brackets and adding poly- as the prefix
  • For example if propene is the alkene monomer used, then the name is polypropene
  • Polyethene is formed by the addition polymerisation of ethene monomers

Addition-Polymerisation-examples, IGCSE & GCSE Chemistry revision notes

Examples of addition polymerisation: polyethene and PVC

Deducing the monomer from the polymer

  • Polymer molecules are very large compared with most other molecule
  • Repeat units are used when displaying the formula
  • To draw a repeat unit, change the double bond in the monomer to a single bond in the repeat unit
  • Add a bond to each end of the repeat unit
  • The bonds on either side of the polymer must extend outside the brackets (these are called extension or continuation bonds)
  • A small subscript n is written on the bottom right hand side to indicate a large number of repeat units
  • Add on the rest of the groups in the same order that they surrounded the double bond in the monomer

Drawing-repeating-units, IGCSE & GSCE Chemistry revision notes

Diagram showing the concept of drawing a repeat unit of a monomer

Deducing the polymer from the monomer

  • Identify the repeating unit in the polymer
  • Change the single bond in the repeat unit to a double bond in the monomer
  • Remove the bond from each end of the repeat unit and the subscript n (which can be placed in front of the monomer)

Deducing monomer structure from repeat units, IGCSE & GCSE Chemistry revision notes

Diagram showing the monomer of the repeat unit of polymer

Exam Tip

For this topic you need to be able to draw diagrams representing monomers and their repeat units.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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