Question

Compare and contrast the key characteristics of anionic polymerization and conventional free-radical polymerization

Answer 1

Similarities between anionic polymerization and free radical polymerization

The main similarity between these two kinds of the polymer is that both polymerization proceeds in three steps. These steps are- initiation, propagation, and termination.

Differences between anionic polymerization and free radical polymerization

1. Anionic polymerization is generally not used on an industrial scale while Free-radical polymerization is the most versatile type of polymerization in the industry.
2. In anionic polymerization, generally, contaminants like water or alcohol are added to terminate the reactions. In free radical polymerization, Chain growth termination occurs via combination or disproportionation
3. Reaction temperature does not affect the anionic polymerization and reactions can be carried out at very low temperatures. Initiation and propagation step in free radical polymerization are strongly affected by the reaction temperature. If we increase the temperature there will be an increase in the rate of chain propagation.
4. Activation energy used for the initiation step of anionic polymerization is much less as compared to free radical polymerization because free radical polymerization requires initiators. These initiators have smaller rate constant so activation energy required is more.
5. Anionic polymerization reactions produce polymers with less branching and have narrow molecular weight distribution while free radical polymerization has less control of molecular weight.