polymerized

Polymerized is an adjective describing a material formed by polymerization. Polymerization is a chemical process in which many small molecules called monomers join to form a macromolecule called a polymer. The resulting polymer typically has a high molecular weight and properties that differ markedly from the monomers.

There are two broad classes of polymerization: chain-growth (addition) polymerization and step-growth (condensation) polymerization. In chain-growth polymerization, activated monomers add sequentially to a growing chain, often initiated by free radicals, cations, or anionic species. This category includes common plastics such as polyethylene, polystyrene, and polyvinyl chloride (PVC). In condensation polymerization, monomers react together with the loss of small molecules (e.g., water, methanol) to form bonds; polymers such as nylons and polyesters are typical examples. Cross-linking can produce networks with different properties, such as rubbers and thermosets.

The term polymerized is used to describe a material that has undergone polymerization, in contrast to its monomeric precursors. The properties of polymerized materials—melting point, strength, elasticity, chemical resistance—depend on monomer type, linkage chemistry, molecular weight, and architecture (linear, branched, cross-linked). Polymerization is foundational to modern materials science and industry, enabling plastics, synthetic fibers, elastomers, and numerous specialty polymers. Advances in catalysts, initiators, and reaction control continue to expand the range of accessible polymers and tailor properties for specific applications.