ketjureaktiopolymeroituminen

Ketjureaktiopolymeroituminen, also known as chain-growth polymerization, is a fundamental process in polymer chemistry where monomers add sequentially to a growing polymer chain. This type of polymerization is characterized by three distinct stages: initiation, propagation, and termination. Initiation involves the formation of an active center, such as a radical, cation, or anion, which then reacts with a monomer to begin the polymer chain. Propagation is the main chain-building step where the active center on the growing chain repeatedly adds monomer units, extending the polymer. Termination occurs when the active center is deactivated, halting further chain growth. This deactivation can happen through various mechanisms, including combination, disproportionation, or chain transfer. The kinetics of chain-growth polymerization are often described by rate constants for each of these stages. This mechanism contrasts with step-growth polymerization, where monomers react with each other to form dimers, trimers, and eventually longer chains, with all molecules capable of reacting at any stage. Common examples of chain-growth polymerization include the polymerization of alkenes like ethylene and propylene, as well as vinyl monomers such as styrene and vinyl chloride. The specific type of active center dictates the classification of chain-growth polymerization into radical, cationic, or anionic polymerization.