Chain propagation

IUPAC definition

Chemical reaction between a chain carrier and a monomer

that results in the growth of a polymer chain and

the regeneration of at least one chain carrier.

Note 1: The recommended symbol for the rate constant for

chain propagation in a homopolymerization is k_p.

Penczek S.; Moad, G. Pure Appl. Chem., 2008, 80(10), 2163-2193

Chain propagation (sometimes referred to as propagation) is a process in which a reactive intermediate is continuously regenerated during the course of a chemical chain reaction. For example in the chlorination of methane, there is a two-step propagation cycle involving as chain carriers a chlorine atom and a methyl radical^[1]

• Cl + CH₄ → HCl + CH₃
• CH₃ + Cl₂ → CH₃Cl + Cl.

In a polymerization reaction, the reactive end-groups of a polymer chain react in each propagation step with a new monomer molecule transferring the reactive group to that last unit.

External links

• IUPAC Gold Book definition: chain-propagating reaction

References

1. chain reaction IUPAC Gold Book