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Such a polymerization, is referred to as a rate-retarded RAFT polymerization. The rate of a RAFT polymerization, that is, the rate of conversion of monomer into polymer, mainly depends on the rate of the Propagation reaction (Figure 5) because the rate of initiation and termination are much higher than the rate of propagation.
The CTA for RAFT polymerization must be chosen cautiously because it has an effect on polymer length, chemical composition, rate of the reaction and the number of side reactions that may occur. The mechanism of RAFT begins with a standard initiation step as homolytic bond cleavage of the initiator molecule yields a reactive free radical.
The expression ‘controlled radical polymerization’ is sometimes used to describe a radical polymerization that is conducted in the presence of agents that lead to e.g. atom-transfer radical polymerization (ATRP), nitroxide-(aminoxyl) mediated polymerization (NMP), or reversible-addition-fragmentation chain transfer (RAFT) polymerization.
The nature of chain transfer reactions is currently well understood and is given in standard polymerization textbooks. Since the 1980s, however, a particularly active area of research has been in the various forms of free radical living polymerizations including catalytic chain transfer polymerization, RAFT, and iodine transfer polymerization ...
Living polymerization: A chain polymerization from which chain transfer and chain termination are absent. Note: In many cases, the rate of chain initiation is fast compared with the rate of chain propagation, so that the number of kinetic-chain carriers is essentially constant throughout the polymerization. [3]
Reversible Addition-Fragmentation Chain-Transfer Polymerization (RAFT): requires a compound that can act as a reversible chain-transfer agent, such as dithio compound. [2] Stable Free Radical Polymerization (SFRP): used to synthesize linear or branched polymers with narrow molecular weight distributions and reactive end groups on each polymer ...
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RAFT polymerization mechanism. Another method of end group removal for the thiocarbonyl containing end-groups of RAFT polymers is the addition of heat to the polymer; this is referred to as thermolysis. One method of monitoring thermolysis of RAFT polymers is by thermogravimetric analysis resulting in a weight-loss of the end group.