addition polymerization

Polymerization reaction in which a single monomer gives rise to a single polymer, with no other reaction products.

Addition polymerization occurs in alkenes, hydrocarbons containing double bonds. The alkenes, such as ethene, are the monomers, the small starting molecules. In addition polymerization, ethene undergoes an addition reaction with itself. As one molecule joins to a second, a long molecular chain is built up. The long molecular chain is called a polymer. In the case of ethene, polythene is formed. It is made up of repeating units of the monomer.