Search results
Results From The WOW.Com Content Network
In polymer chemistry, radical polymerization (RP) is a method of polymerization by which a polymer forms by the successive addition of a radical to building blocks (repeat units). Radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules .
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 is a type of living polymerization involving a conventional radical polymerization which is mediated by a RAFT agent. [8] Monomers must be capable of radical polymerization. [9] There are a number of steps in a RAFT polymerization: initiation, pre-equilibrium, re-initiation, main equilibrium, propagation and termination.
In free radical polymerization, radicals formed from the decomposition of an initiator molecule are surrounded by a cage consisting of solvent and/or monomer molecules. [6] Within the cage, the free radicals undergo many collisions leading to their recombination or mutual deactivation. [5] [6] [9] This can be described by the following reaction:
The termination steps of free radical polymerization steps are of two types: recombination and disproportionation. [2] In a recombination step, two growing chain radicals (denoted by •) form a covalent bond in a single stable molecule. For the example of a vinyl polymer,
Copper-based reversible-deactivation radical polymerization (Cu-based RDRP) is a member of the class of reversible-deactivation radical polymerization. [1] In this system, various copper species are employed as the transition-metal catalyst for reversible activation/deactivation of the propagating chains responsible for uniform polymer chain growth.
Composition drift occurs during the process of free radical copolymerization causing variation in the instantaneous mole fraction of a monomer added to copolymer, therefore altering the chemical composition of the copolymer over the period of conversion.
IUPAC recommends to further simplify "chain-growth polymerization" to "chain polymerization". It is a kind of polymerization where an active center (free radical or ion) is formed, and a plurality of monomers can be polymerized together in a short period of time to form a macromolecule having a large molecular weight.