Formation of Polythene
Specification Point 9.18C:
a) how ethene molecules can combine together in a polymerisation reaction
b) that the addition polymer formed is called poly(ethene) (conditions and mechanisms not required)
- Addition polymers are formed by the joining together of many monomers that contain C=C bonds.
- One of the bonds in each C=C breaks and forms a bond with the adjacent monomer.
- The polymer formed contains only carbon carbon single bonds.
- Many polymers can be made by the addition of alkene monomers.
- 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.
- Polythene is formed by the addition polymerisation of ethene monomers.
Many ethene monomers are joined together in addition polymerisation to form polythene
Specification Point 9.19C:
Describe how other addition polymers can be made by combining together other monomer molecules containing C=C, to include poly(propene), poly(chloroethene) (PVC) and poly(tetrafluoroethene) (PTFE) (conditions and mechanisms not required)
- Addition polymers can be made from any alkene molecule.
- Different monomer molecules produce polymers that have different structures and hence different properties.
- Made from monomers of propene, C3H6.
- Made from monomers of chloroethene, C2H3Cl.
Polytetrafluoroethene (PTFE) also known as Teflon
- Made from monomers of tetrafluoroethene, C2F4.
Specification Point 9.20C:
Deduce the structure of a monomer from the structure of an addition polymer and vice versa
Deducing Monomer Structure
- Identify the repeat units in the polymer.
- Do this visually by looking for identical units that repeat and then highlight or draw a circle around one.
- Change the single bond between the carbon atoms in the repeat unit to a double bond.
- Add on the other atoms or groups that are bonded to each carbon atom, making sure you arrange them in the correct positions.
- You can then draw the monomer out using shorthand notation.
Diagram showing shorthand notation of a monomer deduced from the polymerExample
Deduce the structure of chloroethene from polychloroethene.
Diagram showing the monomer from the repeat unit of an addition polymer (polychloroethene)
Deducing Polymer Structure
- Change the double bond in the monomer to a single bond.
- Add a bond to each end of the repeat unit.
- Draw three or more units together with single bonds between the carbons.
- Add on the other atoms or groups that are connected to each carbon atom, making sure you arrange them in the correct positions.
- If using shorthand notation, make sure you place the extension bonds on either side of the large brackets, adding a subscript n on the right hand side to indicate a large number.
Diagram showing shorthand notation of a polymer deduced from the monomer
Uses of Polymers
Specification Point 9.21C:
Explain how the uses of polymers are related to their properties and vice versa: including poly(ethene), poly(propene), poly(chloroethene) (PVC) and poly(tetrafluoroethene) (PTFE)
- Addition polymers can be engineered to have distinctive properties depending on their intended use.
- This is done by the selection of the monomer.
- Four common polymers are listed with their properties and uses.
Edexcel GCSE Chemistry Notes
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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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