21.8 : 自由基链增长聚合：概述

Chain-growth polymerization, or addition polymerization, is the successive addition of monomers in a growing chain.

Free-radical chain-growth polymerization initiates and proceeds via an unpaired electron from a free-radical intermediate.

The free radical originates from a radical initiator. In the process of adding to the first monomer, the unpaired electron moves to the opposite end of the monomer. As this reactive intermediate sequentially adds to other monomers, the polymer chain grows.

The polymer chain's reactive end, or the propagation site, shifts with each addition to the newly appended monomer. Typically, the number of monomers added to one polymer chain is in the range of one thousand to ten thousand.

To control the chain length of a polymer, a chain transfer reagent is used. It terminates the growth of a polymer chain while simultaneously initiating polymerization by reacting with a monomer.

Inhibitors also can be used to reduce the reactivity of growing polymer chain radicals through stabilization.