polymerised

Polymerised describes a substance that has undergone polymerisation, the chemical process by which monomer units are linked into polymer chains. The resulting material, a polymer, is a large molecule composed of repeating structural units called monomers. The properties of polymerised substances depend on the monomer identity, the linkage chemistry, and the degree of polymerisation.

Polymerisation occurs mainly in two ways. Addition (chain-growth) polymerisation builds polymers by successive addition of monomer units to active centers, typically using free radicals, cations, or anions as initiators. Common addition polymers include polyethylene, polystyrene, and polyvinyl chloride. Condensation (step-growth) polymerisation forms bonds between functional groups with the release of a small molecule such as water or methanol, producing polyamides, polyesters, and polyurethanes.

Polymers can be classified as thermoplastics, which soften when heated and can be re-shaped, or thermosets, which cross-link irreversibly to form rigid networks. They may also be elastomeric. The mechanical and thermal properties of polymerised materials depend on molecular weight, distribution, branching, and cross-link density, as well as processing history.

Industrial polymerisation underpins many materials, including plastics, fibres, coatings, and resins. Key historical developments include the commercialisation of addition polymers in the mid-20th century and advances in controlled polymerisation techniques that allow more precise polymer architectures.