polymeroitumisreaktio

Polymeroitumisreaktio, the Finnish term for polymerization reaction, is the chemical process by which unsaturated monomer units join to form long polymer chains. It is a central concept in polymer chemistry and underpins the manufacture of most plastics, fibers, and numerous biomaterials.

There are two broad classes. In chain-growth (addition) polymerization, an initiator creates an active center that rapidly adds successive monomer units, yielding high-molecular-weight polymers. In condensation (step-growth) polymerization, bifunctional or multifunctional monomers react with release of a small molecule (often water or methanol) and polymer chains grow more slowly as functionality accumulates.

Common mechanisms include free-radical polymerization, as well as ionic pathways (anionic and cationic) and coordination polymerization, which is important for producing stereoregular polymers. In chain-growth processes, initiation, propagation, and termination control the molecular weight and architecture; in step-growth processes, conversion and monomer functionality govern final weight and branching.

Kinetics and thermodynamics influence rate and feasibility. Temperature, monomer concentration, initiator or catalyst activity, and solvent choice affect rate constants and polymer structure. Many polymerizations are exothermic and require thermal or volumetric control to prevent runaway reactions.

Applications encompass a wide range of materials: addition polymers such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride; condensation polymers such as polyamides, polyesters, and polyurethanes; as well as biopolymers like polylactic acid. The choice of method determines properties such as molecular weight, tacticity, crystallinity, and processing behavior.