polymer

In polymerization, small molecules (monomers) join together to make large molecules (polymers). In the polymerization of ethene to polyethene (polythene), electrons are transferred from the carbon-carbon double bond of the ethene molecule, allowing the molecules to join together as a long chain of carbon-carbon single bonds.

Very long-chain molecule made up of many repeated simple units (monomers) linked together by polymerization. There are many polymers, both natural (cellulose, chitin, lignin, rubber) and synthetic (polyethylene and nylon, types of plastic). Synthetic polymers belong to two groups: thermosoftening and thermosetting (see plastic).

The size of the polymer matrix is determined by the amount of monomer used; it therefore does not form a molecule of constant molecular size or mass.