Group transfer polymerization living nature

To study the living nature of this surface initiated polymerization, several groups have performed kinetic studies. " They reported that the nonlinear growth of the polymer brushes as a funetion of irradiation time was mainly attributed to bimolecular termination reaetions, rather than chain transfer to monomer. To avoid irreversible termination reaetions, a strategy to increase the amount of deactivating species by adding tetraethylthiuram disulfide to the polymerization mixture, which is mandatory to provide a controlled radical polymerization behavior, was introduced. ... 

Living ionic polymerization is frequently used to synthesize amphiphilic block copolymers in the absence of irreversible chain transfer and chain termination, where aU polymer chains are instantaneously initiated and grow simultaneously [30]. The presence of counterions in the reaction medium associated witli the propagating chains preserves the electroneutrality of the entire system. However, these living polymerization methods are affected significantly by the nature of the solvent and the presence of water, carbon dioxide, and/or impurities. Moreover, they have limited apphcations for the synthesis of block copolymers with functional groups as side chains. 

Tertiary oxonium ions that are active species in CROP of cyclic ethers are inherently stable (trialkyloxonium salts with stable counterions are commercially available and may be stored without special precautions for prolonged periods of time). Thus, if basic impurities are avoided in CROP of cyclic ethers, there is essentially no irreversible termination. Those polymerization are, however, not classified as living because reversibility of propagation and reversible chain transfer to polymer cause deviations from the ideal situation observed for, for example, anionic vinyl polymerization in which DP = [M]o/[I]o/ molecular weight distribution is close to Poisson distribution and the nature of end-groups may be strictly controlled. As will be discussed in subsequent sections, conditions of living polymerization may be more closely approached if polymerization proceeds by the AM mechanism. 

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