polymerize

Polymerize is the process by which monomer units join to form a polymer, a large molecule made of repeating structural units. Polymerization increases molecular weight and often changes properties such as strength, toughness, rigidity, and melting point. The term can describe a wide range of reactions that build macromolecules from smaller building blocks.

There are two broad classes of polymerization: addition (chain-growth) polymerization and condensation (step-growth) polymerization. In addition polymerization, monomers with unsaturated bonds, such as alkenes, polymerize through initiation, propagation, and termination steps. Initiation may involve free radicals, cations, or anions, and a growing chain adds successive monomer units. Termination can occur by combination, disproportionation, or chain transfer. This path often allows rapid polymer growth and can be highly sensitive to temperature and catalysts.

In condensation polymerization, monomers possessing at least two reactive functional groups form bonds while releasing a small molecule such as water or methanol. This category includes polyesters, polyamides, polyurethanes, and polycarbonates, among others. The reaction typically proceeds with gradual buildup of molecular weight as functional groups react over time.

Controlled or “living” polymerization methods aim to regulate molecular weight and architecture, enabling precise control over polymer length and block copolymer formation. Common polymers produced by these processes include polyethylene, polypropylene, polystyrene, polyvinyl chloride, nylon, polyester, and polyurethane.

Applications span packaging, textiles, automotive, electronics, coatings, and biomedical devices. Environmental considerations address energy use, monomer sourcing, recyclability, and end-of-life management, with ongoing research into biodegradable and more sustainable polymers.