Kaugemõjupolümeeriseerimises

Kaugemõjupolümeeriseerimine, also known as chain-growth polymerization, is a fundamental polymerization mechanism where monomer units are added sequentially to a growing polymer chain. This process typically involves three distinct stages: initiation, propagation, and termination.

Initiation begins with the formation of an active center, which can be a radical, an ion (cation or anion), or an organometallic species. This active center then reacts with a monomer molecule, creating a new active center on the monomer.

Propagation is the chain-lengthening step. The active center at the end of the growing polymer chain reacts with successive monomer units, adding them to the chain and regenerating the active center at the new terminus. This process continues, building a long polymer chain.

Termination occurs when the active center is destroyed, halting the growth of the polymer chain. The mechanism of termination depends on the type of active center involved. For radical polymerization, termination can happen through combination (two growing chains merge) or disproportionation (one chain transfers a hydrogen atom to another, resulting in two saturated chains). For ionic polymerization, termination can occur through reactions with impurities, chain transfer agents, or by other mechanisms specific to the ionic species.

Kaugemõjupolümeeriseerimine is responsible for the synthesis of many common polymers, including polyethylene, polypropylene, polystyrene, and polyvinyl chloride. The control over molecular weight and polymer architecture can be achieved by carefully selecting the initiator, monomer, and reaction conditions.