A polymer is a substance of high relative formula mass, made up of small repeating units.
Poly(ethene)
Poly(ethene) is a polymer made from a very large number of ethene molecules combined together.
The reaction is called a polymerization reaction:
- ethene is the monomer
- poly(ethene) is the polymer
The C=C double bond in ethene is involved in the polymerization reaction. It breaks open to allow ethene molecules to join together to form a single product, so it is an example of an addition reaction. Poly(ethene) is an addition polymer.
Modelling addition polymers
It is too difficult to model a complete addition polymer molecule, as it contains so many atoms. Instead, we show the structure of its repeating unit, the part that is repeated many times. To deduce the structure of a polymer from the monomer:
- Draw the structure of the monomer but use C–C instead of C=C.
- Draw brackets around the structure with a long bond passing through each bracket.
The table shows the structure of ethene and its polymer, poly(ethene).
Modelling addition polymerization
Equations use repeating units to model addition polymerization reactions. The letter n stands for a large number. The polymer, poly(chloroethene) is also known as poly (vinyl chloride), or PVC.
Question
The diagram shows the structure of propene. Deduce the structure of poly(propene) and use this to show an equation for the polymerization of propene.
