Condensation polymer

Condensation polymerization is a form of step-growth polymerization. Linear polymers are produced from bifunctional monomers, i.e. compounds with two reactive end-groups. Common condensation polymers include polyesters, polyamides such as nylon, polyacetals, and proteins.

Polyamides

One important class of condensation polymers are polyamides. They arise from the reaction of carboxylic acid and an amine. Examples include nylons and proteins. When prepared from amino-carboxylic acids, e.g. amino acids, the stoichiometry of the polymerization includes co-formation of water:

n H₂N-X-CO₂H → [HN-X-C(O)]_n + (n-1) H₂O

When prepared from diamines and dicarboxylic acids, e.g. the production of nylon 66, the polymerization produces two molecules of water per repeat unit:

n H₂N-X-NH₂ + n HO₂C-Y-CO₂H → [HN-X-NHC(O)-Y-C(O)]_n + (2n-1) H₂O