CIE IGCSE Chemistry

Revision Notes

14.3.2 Synthetic Polymers

Plastics & Man-Made Fibres

Plastics, nylon and terylene

  • These are synthetic polymers with many uses
  • Nylon is a copolymer used to produce clothing, fabrics, nets and ropes
  • Terylene is a polyester made from monomers which are joined together by ester links
  • Terylene is used extensively in the textile industry and is often mixed with cotton to produce clothing
  • Synthetic polymerisation also produces plastics that have many different uses in today’s society

Uses of plastics

Uses of plastics table, IGCSE & GCSE Chemistry revision notes

 

Non-biodegradable plastics

  • These are plastics which do not degrade over time or take a very long time to degrade, and cause significant pollution problems
  • In particular plastic waste has been spilling over into the seas and oceans and is causing huge disruptions to marine life
  • In landfills waste polymers take up valuable space as they are non-biodegradable so microorganisms cannot break them down. This causes the landfill sites to quickly fill up
  • Polymers release a lot of heat energy when incinerated and produce carbon dioxide which is a greenhouse gas that contributes to climate change
  • If incinerated by incomplete combustion, carbon monoxide will be produced which is a toxic gas that reduces the capacity of the blood to carry oxygen
  • Polymers can be recycled but different polymers must be separated from each other which is a difficult and expensive process
Extended Only

Addition & Condensation Polymers & Deducing Structures

Addition polymerisation

  • 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

 

Addition-Polymerisation-examples, IGCSE & GCSE Chemistry revision notesExamples of addition polymerisation: polythene and PVC

 

Condensation polymerisation

  • Condensation polymers are formed when monomer molecules are linked together with the removal of a small molecule, usually water
  • Condensation polymerisation usually involves two different monomers, each one having a functional group on each end
  • Hydrolysing (adding water) to the compound in acidic conditions usually reverses the reaction and produces the monomers by rupturing the peptide link

 

Hydrolysis & Condensation, IGCSE & GCSE Chemistry revision notesCondensation produces the polyamide which is ruptured at the link by hydrolysis in the reverse reaction

 

Deducing the monomer from the polymer

  • Polymer molecules are very large compared with most other molecules
  • Repeat units are used when displaying the formula:
  • 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

 

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

 

Deducing monomer structure from repeat units, IGCSE & GCSE Chemistry revision notesDiagram showing how to deduce the structure of a monomer from a repeat unit

 

 

Example: Deducing the structure of chloroethene from a repeat unit of Poly(chloroethene)

Deducing chloroethene structure, IGCSE & GCSE Chemistry revision notesDiagram showing the monomer from the repeat unit of an addition polymer (polychloroethene)

 

Formation of nylon

  • Nylon is a polyamide made from dicarboxylic acid monomers (a carboxylic with a -COOH group at either end) and diamines (an amine with an -NH2 group at either end)
  • Each -COOH group reacts with another -NH2 group on another monomer
  • An amide linkage is formed with the subsequent loss of one water molecule per link

 

Forming-Nylon, IGCSE & GCSE Chemistry revision notesThe condensation reaction in which the polyamide Nylon is produced

 

Formation of terylene

  • Terylene is a polyester made from dicarboxylic acid monomers (a carboxylic with a -COOH group at either end) and diols (an alcohol with an -OH group at either end)
  • Each -COOH group reacts with another -OH group on another monomer
  • An ester linkage is formed with the subsequent loss of one water molecule per link

 

Forming-Terylene, IGCSE & GCSE Chemistry revision notesThe condensation reaction in which the polyester Terylene is produced

Exam Tip

You should be able to draw the box diagrams representing polymers where each box represents a part of the repeating hydrocarbon chain.

The functional groups on the monomers and the link formed in the polymers are the important parts and must be clearly drawn.

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.
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