The long chain-like macromolecules in nylon are made by the joining together of many smaller molecules called monomers. The monomers for nylon 6-6 are adipic acid and hexamethylene diamine.
Adipic acid contains carboxylic acid groups, shown in red. Since there are two carboxylic acid groups, adipic acid is called a diacid. Hexamethylene diamine contains amine groups, shown in blue. Since there are two amine groups, hexamethylene diamine is called a diamine. The carboxylic acid groups and the amine groups react together; when these molecules join they become nylon polymer.
To make nylon polymer, a molecule of hexamethylene diamine and adipic acid join together as shown below. The atoms shown in blue will be eliminated, and end up as a water (H2O) molecule. The rest of the adipic acid molecule and the hexamethylene diamine molecule become joined together as the larger molecule shown below.
This new big molecule has an acid group at one end and an amine group at the other:
These groups can react just like the acid and amine groups on adipic acid and hexamethylene diamine will. This will make an even bigger molecule, of course. It can react to make a molecule larger still. This reacting goes on until the molecules have grown into very long chains, which we draw like this:
But there's more to making long chains of nylon. Visit the following pages to find out more!
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Nylon Salt
Acetic Acid and Molecular Weight
