Kettenabbruchmethode

The Kettenabbruchmethode, or chain termination method, is a concept primarily discussed in the context of polymer chemistry and radical polymerization. It refers to the process by which a growing polymer chain stops elongating. In radical polymerization, a chain grows through the sequential addition of monomers to a radical center. This growth can be interrupted by several mechanisms, collectively known as chain termination.

One common mechanism is combination, where two growing radical chains encounter each other and their unpaired electrons combine to form a single, stable covalent bond. This results in a single, longer polymer chain. Another mechanism is disproportionation, where a hydrogen atom is transferred from one growing radical chain to another. This results in two stable polymer chains, one with a saturated end and the other with an unsaturated end.

In addition to these bimolecular termination events, chain termination can also occur intramolecularly or through reactions with impurities or inhibitors present in the reaction mixture. The rate and efficiency of these termination processes significantly influence the molecular weight and molecular weight distribution of the resulting polymer. Understanding chain termination is crucial for controlling the polymerization process and achieving desired polymer properties.