Anionic Addition Polymerization - Termination

Termination

Anionic addition polymerizations have no formal termination pathways because proton transfer from solvent or other positive species does not occur. However, termination can occur through unintentional quenching due to trace impurities. This includes trace amounts of oxygen, carbon dioxide or water. Intentional termination can occur through the addition of water or alcohol. Another method of termination, chain transfer, can occur when an agent can act as a Brønsted acid. In this case, the pKa value of the agent is similar to the conjugate acid of the propagating carbanionic chain end. Spontaneous termination occurs because the concentration of carbanion centers decay over time and eventually results in hydride elimination. Polar monomers are more reactive because they are stabilized by their polar substituents. These polar substituents can react with nucleophiles which results in termination as well as side reactions that compete with both initiation and propagation.