CIE A Level Chemistry (9701) 2019-2021

Revision Notes

7.7.3 Characteristics of Condensation Polymers

Condensation Polymer Characteristics

Characteristics of condensation polymerisation

  • Condensation polymers characteristically have either amide or ester links in their polymer backbone
  • When monomers react together, a small molecule (eg. water or hydrochloric acid) is often expelled

Polyesters

  • A diol and a dicarboxylic acid are required to form a polyester
    • A diol contains 2 -OH groups
    • A dicarboxylic acid contains 2 -COOH groups
  • When the polyester is formed, one of the -OH groups on the diol and the hydrogen atom of the -COOH are expelled as a water molecule (H2O)
  • The resulting polymer is a polyester
  • Terylene is an example of a polyester

Expulsion of a water molecule in this condensation polymerisation forms the polyester called Terylene (PET)

Polyamides

  • The amide link (also called a peptide link in biochemistry terms) is the defining feature of a polyamide
  • Amides consist of a R’C=O carbonyl linked to a -NHR”
  • A diamine and a dicarboxylic acid are required to form a polyamide
    • A diamine contains 2 -NH2 groups
    • A dicarboxylic acid contains 2 -COOH groups
  • Dioyl dichlorides can also used to react with the diamine instead of the acid
    • A dioyl chloride contains 2 -COOCl groups
  • This is a more reactive monomer than dicarboxylic acid. However, a more expensive alternative

Polymerisation - Polyamide Monomers (2), downloadable AS & A Level Chemistry revision notes

The monomers for making Polyamides

This shows the expulsion of a small molecule as the amide link forms

Nylon 6,6

  • Nylon 6,6 is a synthetic polyamide
  • Its monomers are 1,6-diaminohexane and hexane-1,6-dioic acid
    • The ‘6,6’ part of its name arises from the 6 carbon atoms in each of Nylon 6,6 monomers

Polymerisation - Making Nylon 6,6, downloadable AS & A Level Chemistry revision notes

Nylon 6,6 is a synthetic polyamide made using diamine and dicarboxylic acid monomers

Nylon 6

  • Nylon 6 is a slight variation on Nylon 6,6
  • The monomer is a cyclic amide molecule – Caprolactam
  • This monomer opens its ring structure when polymerised and adds to other caprolactam monomers
  • The amide link in the original monomer is preserved and can be seen along the main backbone of the Nylon 6 polymer chain

Kevlar

  • Kevlar is another example of a polymer formed through condensation polymerisation
  • The polymer chains are neatly arranged with many hydrogen bonds between them
  • This results in a strong and flexible polymer material with fire resistance properties
  • These properties lend Kevlar to a vital application in bullet-proof vests
  • The monomers used to make Kevlar
    • 1,4-diaminobenzene
    • Benzene-1,4-dicarboxylic acid
  • As seen with Nylon, a dioyl chloride can be used instead of the acid as well (benzene-1,4-dioyl chloride)

Kevlar is made using a diamine and dicarboxylic acid monomers

Making Proteins

  • Proteins are vital biological molecules with varying functions within the body
  • They are essentially polymers made up of amino acid monomers
  • Amino acids have an aminocarboxylic acid structure
  • Their properties are governed by a branching side group – the R group

Amino acids contain an amine group, an acid group and a unique R group

  • Different amino acids are identified by their unique R group
  • The names of each amino acid is given using 3 letters
  • For example Glutamine is known as ‘Gln’

 

  • Dipeptides can be produced by polymerising 2 amino acids together
    • The amine group (-NH2) and acid group (-COOH) of each amino acid is used to polymerise with another amino acid
  • Polypeptides are made through polymerising more than 2 amino acids together

Dipeptides and polypeptides are formed by polymerising amino acid molecules together

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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