Polymers

• Polymer: a large molecule made up of many repeating units or monomers

• Addition polymers can be formed by repeated addition reactions between unsaturated hydrocarbons, such as alkenes

• Unlike in condensation polymerisation, the polymer itself  is the only product formed during addition polymerisation

Monomer                          Polymer                            Repeating Unit                              Uses

• Condensation polymers are formed by a condensation reaction between two different functional groups.

• For example, polypeptides are formed from amino acids, which each contain an amine group and a carboxylic acid group

• Polyesters are fromed from a dicarboxylic acid and a diol: a compound containing two hydroxyl groups

• Poly(alkenes) are chemically inert and are therefore non-biodegradable

•  Poly(alkenes) can become more biodegradable if, for example, starch is incorporated into poly(ethene) used for carrier bags. Starch is hydrolysed by microorganisms, which breaks down the carrier bag

• Polyesters and polyamides are biodegradable. Methyl ethanoate can be hydrolysed to produce methanol and ethanoic acid, for example

• Polyesters are readily hydrolysed by strong alkalis, and polyamides are readily hydrolysed by strong acids. Certain enzymes can also be used for hydrolysis

Advantages

• Protection of useful hydrocarbons for the future
• Reduces landfill

Disadvantages

• Difficult and expensive; polymers are often mixed with paints or dyes and must be separated

Landfill

• Limited amount of land available

• Landfill sites fill up very quickly, especially when non-biodegradable polymers are disposed of

Incineration

• Carbon dioxide, a greenhouse gas, is produced

• Toxic gases can be produced unless polymers are incinerated at very high temperatures