Chain propagation

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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 kp.

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[edit]


  1. ^ chain reaction IUPAC Gold Book