Living radical polymerization deactivator

These are two possibilities for the polymerization of MA deviated from the ideal living radical polymerization (i) the chain end of poly(MA) formed primary radical termination with a DC radical does not dissociate or dissociates at an unfavorable position like 41 (ii) bimolecular termination leading to the deactivation of the iniferter sites occurs preferentially to the primary radical termination with the DC radical which reproduces the iniferter site. 

Living radical polymerization (LRP) has attracted growing attention as a powerful synthetic tool for well-defined polymers 1,2). The basic concept of LRP is the reversible activation of the dormant species Polymer-X to the propagating radical Polymer (Scheme la) 1-3). A number of activation-deactivation cycles are requisite for good control of chain length distribution. 

Jenkins, A.D., Jones, R.G., Moad, G., 2010. Terminology for reversible-deactivation radical polymerization previously called controlled radical or living radical polymerization. Pure Appl. Chem. 82 (2), 483 91. 

Fig. 1 Main activation-deactivation equilibria in controUed/Living radical polymerization. The first two are reversible termination reactions and the last two are reversible chain transfer reactions. Pj stands for a macroradical with i monomer subunits. In the initial control agent, the polymer chain is replaced by a low molar mass leaving/initiating group, often referred to as...

Klumperman and coworkers [259] observed that while it is lately quite common to treat living radical copolymerization as being completely analogous to its radical counterpart, small deviatiOTis in the copolymerization behavior do occur. They interpret the deviations on the basis of the reactions being specific to controlled/living radical polymerization, such as activation—deactivation equilibrium in ATRP. They observed that reactivity ratios obtained from atom transfer radical copolymerization data, interpreted according to the conventional terminal model deviate from the true reactivity ratios of the propagating radicals. 

Remarkably, the same key concept applies in living radical polymerizations. It has been suggested that the term temporary deactivation is more appropriate than reversible termination, to emphasize control (20). 

Nitroxide Mediated Living Radical Polymerization. Another controlled radical polymerization developed in recent years is stable free radical mediated polymerization (SFRP), also called as nitroxide mediated radical polymerization (NMP) (78,131). This type polymerization can be reahzed through reversible deactivation of growing radicals by stable radical such as 2,2,6,6-tetramethyl-piperidinyloxy (TEMPO). 

Narrow polydispersity, in principle, may be obtained in a free-radical polymerization process, if the process proceeds by a living mechanism, with no premature termination, and if all the propagating chains are initiated at about the same time, similar to what occurs in an anionic polymerization process (Georges et al., 1993). A variety of living radical polymerization systems have been developed in recent years. These are based on either reversible termination or reversible transfer of chain radical for which four principal mechanisms have been put forward (1) Polymerization with reversible termination (deactivation) of growing chains by coupling, the best example in this... 

Terminology for reversible-deactivation radical polymerization previously called controlled radical or living radical polymerization Pure Appl. Chem. 82 (2010) 483. 

Several controlled and living radical polymerization techniques are available today. All are based on the reversible deactivation of growing chains. Consequently, a 2010 lUPAC recommendation proposes the term controlled reversible-deactivation radical polymerization (CRDRP) for polymerizations previously referred to as controlled radical (CRP) or living radical (LRP) polymerization. Nevertheless, due to their widespread acceptance, the terms controlled/living radical polymerization will also be used in this chapter. 

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