Polyymerisaatio

Polyymerisaatio, a term sometimes encountered in Finnish-language texts, refers to the chemical process of joining monomer units into a polymer. The standard Finnish spelling is polymerisaatio. The process is broadly divided into chain-growth polymerization and step-growth polymerization, depending on how reactive centers propagate the chain.

In chain-growth polymerization, an active center is generated at initiation and rapidly adds monomer units (propagation) until termination. This category includes radical, anionic, and cationic polymerizations. Radical polymerization, often initiated by organic peroxides or azo compounds, is widely used for vinyl monomers such as ethylene, propylene, and styrene, producing polymers like polyethylene and polystyrene. Anionic and cationic variants enable living/controlled polymerization in some cases, allowing narrower molecular weight distributions and architectures.

Step-growth polymerization proceeds by reaction between multifunctional monomers, where growth occurs through stepwise condensation or polyaddition without a discrete growing radical site. Condensation polymers (polyesters, polyamides, polyurethanes) form with evolution of a small molecule (for example water or methanol). Step-growth processes often require stoichiometric balance and higher conversions before high molecular weights are reached.

Catalysts, solvents, temperature, and monomer functionality govern rate and outcome. Industrial polymerization uses Ziegler-Natta and metallocene catalysts for polyolefins, and radical polymerization for a broad range of plastics and resins. Modern techniques such as reversible-deactivation radical polymerization (RAFT, ATRP) enable living polymerization and complex architectures like block and graft copolymers.

Polyymerisaatio is central to materials science, enabling the production of plastics, fibers, elastomers, and coatings, with ongoing research aimed at improving efficiency, control, and sustainability.