Acid and base hydrolysis of polymers

In a nutshell

Polymers can be hydrolysed to their monomers. Hydrolysis occurs faster in the presence of an acid or a base catalyst.

Equations

These are general chemical equations. You will need to be able to use these when you write equations for specific substances.

​$$polyester \,+\, water \xrightleftharpoons[reflux]{H^+} dicarboxylic \space acid \,+\,diol \\ \ \\polyamide \,+\, water \xrightleftharpoons[reflux]{H^+} dicarboxylic \space acid \,+\, diamine \\ \ \\polyester \,+\, hydroxide\, \,\xrightarrow{reflux}\,\, dicarboxylate \, +\,diol \\ \ \\polyamide \,+\, hydroxide\, \,\xrightarrow{reflux}\,\, dicarboxylate \, +\, diamine$$​​

Hydrolysis

Hydrolysis is the breaking of a molecule using water. Polymers can be hydrolysed in the presence of a catalyst to increase the rate of reaction. Hydrolysis using water only is a slow process.

The products of hydrolysis are the monomers (or monomer derivatives) of the polymer. Either two products will form or in the case of a complex polymer one product will be produced which contains two different functional groups.

Acid hydrolysis

Polymers can be split in the presence of water and an acid catalyst, such as dilute sulfuric acid.

​$$polyester \,+\, water \xrightleftharpoons[reflux]{H^+} dicarboxylic \space acid \,+\,diol \\ \ \\polyamide \,+\, water \xrightleftharpoons[reflux]{H^+} dicarboxylic \space acid \,+\, diamine$$

If there is an excess amount of hydrogen ions, hydrolysis of polyamide will lead to the formation of an ammonium ion/salt due to the protonation of the nitrogen.

General

Example

Base hydrolysis

Polymers can be split in the presence of water and a base catalyst, such as sodium hydroxide.

​$$polyester \,+\, hydroxide\, \,\xrightarrow{reflux}\,\, dicarboxylate \, +\,diol \\ \ \\polyamide \,+\, hydroxide\, \,\xrightarrow{reflux}\,\, dicarboxylate \, +\, diamine$$​​

General

​​Example