Condensation polymers - Higher
Long molecules (such as nylon, Kevlar or polyester) produced during condensation polymerisation. form in a different way to Large molecule formed in addition reactions between unsaturated monomer molecules.:
| Condensation polymerisation | Addition polymerisation |
| Two types of monomer | One type of monomer |
| Monomer must have two functional groups (one on each end) | Monomer must have a C=C bond |
| Two products are formed - the polymer plus many small molecules (usually water) | The only product is the polymer |
| Condensation polymerisation | Two types of monomer |
|---|---|
| Addition polymerisation | One type of monomer |
| Condensation polymerisation | Monomer must have two functional groups (one on each end) |
|---|---|
| Addition polymerisation | Monomer must have a C=C bond |
| Condensation polymerisation | Two products are formed - the polymer plus many small molecules (usually water) |
|---|---|
| Addition polymerisation | The only product is the polymer |
Forming polyesters
An A type of organic compound formed in the reaction between an alcohol and a carboxylic acid. forms when an An organic compound containing a hydroxyl group, -OH. The 'alcohol' in alcoholic drinks is ethanol, produced by the fermentation of sugars and found in wines, spirits and beers. reacts with a A homologous series of compounds that contain the carboxyl functional group, -COOH.. For example:
ethanol + ethanoic acid 鈫 ethyl ethanoate + water
CH3CH2OH + CH3COOH 鈫 CH3COOCH2CH3 + H2O
Ethyl ethanoate is an ester. Notice that one water molecule forms when one ester molecule forms.
A Condensation polymer made from two types of monomer, one with two 鈥揙H groups and one with two 鈥揅OOH groups. forms from two different Small molecule, usually containing a C=C bond, that can join end to end with other monomers to form a polymer molecule.:
- a 'dicarboxylic acid' which contains two carboxylic acid groups, -COOH
- a 'diol' which contains two alcohol groups, -OH
For example, PET is a polyester made from terephthalic acid and ethane-1,2-diol. It is used to make drinks bottles and fleeces.
Notice that:
- both ends of each monomer molecule can react with another monomer molecule
- one molecule of water is formed every time an ester link is formed
- one A part of a polymer that would make a complete polymer molecule if many of them were joined end to end. is made from two different monomer molecules
The monomers and polymer can be represented by simplified 'block diagrams'. In these diagrams, only the functional groups are shown in detail. The rest of the molecule is shown as a shaded block, or with the symbol R (R1 and R2 may be used if the parts differ from one another).
Forming polyamides
A common synthetic polyamide is nylon. Proteins are naturally forming polyamides.
A polyamide is formed from two monomers:
- a diamine (with an NH2 group on each end)
- a dicarboxylic acid (with a COOH group on each end)
Question
Draw the displayed and structural formula of the two monomers that would make this condensation polymer.