Addition Polymers (Edexcel GCSE Chemistry)

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