Britannica Sources used in this answer

Why does condensation polymerization often produce water as a by-product?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram illustrating a homopolymer arrangement using polyvinyl chloride as an example, showing a chain of identical repeating vinyl chloride units with the chemical structure highlighted. — polymer Industrial polymers are synthesized from simple compounds joined together to form long chains. For example, polyvinyl chloride is an industrial homopolymer synthesized from repeating units of vinyl chloride.

In chemistry, condensation polymerization is a process where monomers combine to form a polymer while simultaneously eliminating a small molecule, such as water.12

This occurs because the reaction involves the joining of two or more reactive atomic groupings—such as alcohol, acid, or amine groups—found on the monomer molecules. As these functional groups react to form a new, stable covalent chemical bond between the monomers, the atoms that are not part of the new linkage are released as a byproduct.342

For instance, in the formation of certain polyesters or resins, the reaction between specific functional groups results in the loss of water as the molecules "condense" into a larger, chainlike or network structure. This distinguishes condensation polymerization from addition polymerization, where monomers combine without the loss of any by-products.352