Addition Polymers (Edexcel GCSE Chemistry)
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Formation of Polythene
- 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
- Poly(ethene) is formed by the addition polymerisation of ethene monomers and is most commonly called polythene
Ethene monomers join up to form poly(ethene)
Other Addition Polymers
- Other addition polymers are made from alkene monomers with different atoms attached to the monomer such as chlorine, fluorine or a methyl 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 poly(propene)
Further examples of addition polymerisation: poly(chloroethene)(PVC), poly(propene) and poly(tetrafluorethene)(PTFE)
Deducing Structures
Deducing the polymer from the monomer
- Polymer molecules are very large compared with most other molecule
- Repeat units are used when displaying the formula
- To draw a repeat unit, 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
- Add on the rest of the groups in the same order that they surrounded the double bond in the monomer
Diagram showing the concept of drawing a repeat unit of a monomer
Deducing the monomer from the polymer
- 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 (which can be placed in front of the monomer)
Diagram showing the monomer of the repeat unit of polymer
Uses of Polymers
- 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
Uses of Common Polymers Table
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