Comparison between Free-Radical and Controlled Radical Polymerization

Free Radical Polymerization Controlled Radical Polymerization

Initiation can be slow or fast depending on the chosen initiator and temperature.

Initiation (radical generation) occurs preferably in a very short period of time.

Propagation (chain growth) is very fast and time dependent.

Propagation is much slower and less time dependent.

Transfer reactions occur (frequently) causing a broadening of the MW distribution.

Tranfer reactions are almost absent resulting in a narrower MW distribution.

Radical life-time is very short.

Radical life-time is very long.

Essentially all chain are terminated (dead) after complete consumption of monomer.

Only a small portion of polymer chains are irreversibly terminated, that is, the majority is "living".

Activation/deactivation reactions are absent.

Activation/deactivation reactions occur frequently (most chains are dormant).

Concentration of growing chains is very high (10-7 – 10-9 M).

Concentration of growing chains is very low (10-1 – 10-4 M).

Poor control over the molecular architecture and molecular weight.

Good control over the molecular architecture and molecular weight

  • Summary

  • Free-Radical Polymerization (FRP)

    is the most versatile type of chain-growth polymerization and is suitable for almost all vinyl monomers but allows for less control of molecule weight, chain architecture and polydispersity.

  • Controlled Radical Polymerization (CRP)

    is based on reversible activation-deactivation of propagating chains. This method allows for good control over molecular weight distribution and chain architecture.