Addition polymers
A A large molecule formed from many identical smaller molecules known as monomers. is a long chain molecule made up of A part of a polymer that would make a complete polymer molecule if many of them were joined end to end.. A polymer can be made synthetically by combining many small molecules, known as monomers.
Monomers can be based on alkenes produced from the The breaking down of large hydrocarbon molecules into smaller, more useful hydrocarbon molecules by vaporising them and passing them over a hot catalyst. of Mixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms.. Large molecule formed in addition reactions between unsaturated monomer molecules. form when the double bond in alkene monomers open up, allowing more monomers to join together to create a long chain.
For example, poly(ethene) is a polymer made from a very large number of ethene A collection of two or more atoms held together by chemical bonds. combined together.
The reaction is called a Reaction in which monomer molecules combine together to form larger polymer molecules.:
- ethene is the Small molecule, usually containing a C=C bond, that can join end to end with other monomers to form a polymer molecule.
- poly(ethene) is the polymer
The C=C double bond in ethene is involved in the polymerisation reaction. It allows ethene molecules to join together to form a single A substance formed in a chemical reaction., so it is an example of an Chemical reaction in which unsaturated monomers (small molecules) join together by addition reactions to produce a polymer (long molecule)..
There is a wide range of addition polymers, known more generally as plastics:
| Monomer | Polymer | Common name | Uses |
| Ethene | Poly(ethene) | Polythene | Carrier bags, food packaging |
| Chloroethene | Poly(chloroethene) | PVC (from its old name, polyvinylchloride) | Window frames, doors |
| Propene | Poly(propene) | Polypropylene | Car bumpers, toys |
| Tetrafluoroethene | Poly(tetrafluoroethene) | PTFE | Non-stick coating in frying pans |
| Monomer | Ethene |
|---|---|
| Polymer | Poly(ethene) |
| Common name | Polythene |
| Uses | Carrier bags, food packaging |
| Monomer | Chloroethene |
|---|---|
| Polymer | Poly(chloroethene) |
| Common name | PVC (from its old name, polyvinylchloride) |
| Uses | Window frames, doors |
| Monomer | Propene |
|---|---|
| Polymer | Poly(propene) |
| Common name | Polypropylene |
| Uses | Car bumpers, toys |
| Monomer | Tetrafluoroethene |
|---|---|
| Polymer | Poly(tetrafluoroethene) |
| Common name | PTFE |
| Uses | Non-stick coating in frying pans |
Modelling addition polymers
It is too difficult to model a complete addition polymer molecule, as it contains many The smallest part of an element that can exist.. 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鈥揅 instead of C=C
- draw brackets around the structure with a long bond passing through each one
This table shows the structure of ethene and its polymer:
Modelling addition polymerisation
Equations use repeating units to model addition polymerisation reactions. The letter 'n' stands for a large number.
Question
The diagram shows the structure of propene. Deduce the structure of poly(propene), and use this to show an equation for the polymerisation of propene.
Question
The diagram shows the structure of tetrafluoroethene. Deduce the structure of poly(tetrafluoroethene), and use this to show an equation for the polymerisation of tetrafluoroethene.