Definition of chain transfer

The abstraction, by the radical end of a growing chain-polymer, of an atom from another molecule. The growth of the polymer chain is thereby terminated but a new radical, capable of chain propagation and polymerization, is simultaneously created. For the example of alkene polymerization cited for a chain reaction, the reaction

RCH2C.HPh + CCl4 RCH2CHClPh + Cl3C.

represents a chain transfer, the radical Cl3C. inducing further polymerization:

H2C=CHPh + Cl3C. Cl3CCH2C.HPh

Cl3CCH2C.HPh + H2C=CHPh Cl3CCH2CHPhCH2C.HPh

The phenomenon occurs also in other chain reactions such as cationic polymerization. See also telomerization.