How To Draw Repeat Units Of Polymers

Edexcel IGCSE Chemistry

Revision Notes

Monomers

Polymers are large molecules ofhigh relative molecular mass and are made by linking together large numbers of smaller molecules calledmonomers
Each monomer is arepeat unit and is connected to the adjacent units viacovalent bonds
Polymerisation reactions usually requirehigh pressures and the use of acatalyst
Many everyday materials such as resins, plastics, polystyrene cups, nylon etc. are polymers
These are manufactured and are called synthetic polymers
Nature also produces polymers which are callednatural orbiological polymers

Polymers - Basic, IGCSE & GCSE Chemistry revision notes

Diagram showing how lots of monomers bond together to form a polymer

Drawing Polymers

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 containingsingle bonds only
Many polymers can be made by the addition of alkene monomers
Others are made from alkene monomers with different atoms attached to themonomer 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 theprefix
For example if propene is the alkene monomer used, then the name ispolypropene
Polyethene is formed by the addition polymerisation of ethene monomers

Examples of Addition Polymers 1, downloadable IGCSE & GCSE Chemistry revision notes

Examples of addition polymerisation: polyethene and PVC

Deducing Monomers & Repeat Units

Deducing the monomer from the polymer

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 asingle bond in the repeat unit
Add a bond to each end of the repeat unit
The bonds on either side of the polymer mustextend outside the brackets (these are called extension or continuation bonds)
A smallsubscript 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 thesame order that they surrounded the double bond in the monomer

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

Diagram 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 adouble bond in the monomer
Remove the bond from each end of the repeat unit and the subscriptn (which can be placed in front of the monomer)

Deducing monomer structure from repeat units, IGCSE & GCSE Chemistry revision notes

Diagram showing the monomer of the repeat unit of polymer

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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.