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In polymer chemistry, free-radical polymerization (FRP) is a method of polymerization by which a polymer forms by the successive addition of free-radical building blocks (repeat units). Free radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules .
4,4′-Azobis(4-cyanopentanoic acid) (ACPA) is a free radical initiator used in polymer synthesis. [1] ACPA is a water-soluble initiator used in both heterogeneous and homogeneous free-radical polymerizations. It is used as an initiator in reversible addition−fragmentation chain transfer polymerization (RAFT).
In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical reactions. [1] These substances generally possess weak bonds—bonds that have small bond dissociation energies. Radical initiators are utilized in industrial processes such as polymer synthesis.
Living free radical polymerization is a type of living polymerization where the active polymer chain end is a free radical. Several methods exist. Several methods exist. IUPAC recommends [ 1 ] to use the term " reversible-deactivation radical polymerization " instead of "living free radical polymerization", though the two terms are not synonymous.
RAFT polymerization can be performed by adding a chosen quantity of an appropriate RAFT agent to a conventional free radical polymerization. Usually the same monomers, initiators, solvents and temperatures can be used.
These techniques involved catalytic chain transfer polymerization, iniferter mediated polymerization, stable free radical mediated polymerization (SFRP), atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization, and iodine-transfer polymerization. In "living" radical polymerization (or ...
Heating a reaction can result in radical initiation of the substrate(s). [6] In the presence of heat, a monomer can self-initiate and react with other monomers or pairs of monomers. This process is called spontaneous polymerization and requires a lot of heat to occur (up to 200°C). [4]
Another example of a radical reaction that can be initiated by AIBN is the anti-Markovnikov hydrohalogenation of alkenes. AIBN has also been used as the radical initiator for Wohl–Ziegler bromination. The AIBN-derived 2-cyano-2-propyl radical abstracts the hydrogen from tributyltin hydride. [5]