CIE A Level Chemistry (9701) exams from 2022

Revision Notes

7.7.4 Predicting & Deducing the Type of Polymerisation

Predicting Type of Polymerisation

  • When a set of monomers are given in an exam question, the type of polymerisation can be determined
  • Firstly, it’s important to identify the key functional groups in the monomers

Addition polymerisation

  • If the monomer/s contain a C=C double bond, they will polymerise through addition polymerisation
  • The double bond can open up in order to add more monomers either side of the starting monomer
  • This type of polymerisation makes (poly)alkenes

Addition polymerisation of one alkene monomer is polymerised, a (poly)alkene is formed

  • (Poly)alkenes can be produced if there are 2 or more alkene monomers as well
  • When more than one monomer is used for addition polymerisation, the resulting product is known as a copolymer

  

Two or more different alkene monomers can also be polymerised in Addition polymerisation. This gives a co-polymer

Condensation polymerisation

  • Condensation polymerisation makes polyamides and polyesters
  • When looking to identify this type of polymerisation, there are some key functional groups to be aware of

Monomers for condensation polymers table

Exam Tip

  • As well as the functional groups to be aware of, know that a small molecule is expelled when the polymer is formed
  • Identify 2 functional groups that can react together to produce either a polyamide or a polyester
  • There are instances where both of the functional groups are on the same monomer molecule
    • For example amino acid molecules contain an amine group (-NH2) and a carboxylic acid group (-COOH) therefore it can polymerise to produce a polyamide

Deducing Type of Polymerisation

  • The type of polymerisation can be determined by considering the structure of the polymer backbone

Identifying addition polymerisation

  • The polymer backbone of an addition polymer does not contain functional groups
  • The backbone of the polymer is generally a chain of carbon atoms
  • There may be sidechains branching off from the backbone
  • Some examples of side chains are benzene rings, nitrile groups (-CN) and halogen atoms (-F/-Cl/-Br/-I)

Addition polymers are identified using the plain carbon chain as the polymer backbone

Identifying condensation polymerisation

  • A condensation polymer can be identified by functional groups on the polymer backbone
  • Polyesters contain ester links and polyamides contain amide/peptide link on the backbone itself

Condensation polymers are identified using function groups that form parts of the polymer backbone

Exam Tip

  • Different sections of polymer chains may be formed using various type of polymerisation
  • In an exam, you may be given a section of a polymer and asked to determine the type of polymerisation used to form that section
  • Firstly, look at the polymer backbone
    • If there are functional groups along the backbone, that section was made using condensation polymerisation
    • If there are no functional groups along the backbone, addition polymerisation was used

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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