Britannica Sources used in this answer

How does addition polymerization differ from condensation polymerization?

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, polymerization is the process by which small molecules, known as monomers, chemically combine to form large chainlike or network molecules called polymers. The primary distinction between addition and condensation polymerization lies in the formation of by-products.1

Addition Polymerization

Addition polymerization occurs when monomers react to form a polymer without the creation of any by-products. This process is characteristic of monomers that contain a double bond or a strained ring structure. These reactions are typically facilitated by catalysts, which help control the structural properties of the resulting polymer.213

Condensation Polymerization

In condensation polymerization, each step of the reaction is accompanied by the elimination of a small molecule, such as water or hydrochloric acid. This process typically involves monomers that possess two or more reactive functional groups, such as carboxylic acids, alcohols, or amines, which react to form new linkages like esters or amides.4153