CIE A Level Chemistry复习笔记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

7.7-Polymerisation-Polymers-From-One-Alkene-Monomer

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

7.7-Polymerisation-Copolymers-From-MonomersTwo 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 table7.7-Polymerisation-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)

7.7-Polymerisation-Examples-of-Addition-Polymers

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

7.7-Polymerisation-Examples-of-Condensation-Polymers

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

 

 

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