Unimolecular Alkoxyamines

A number of unimolecular alkoxyamines containing alkyne or azide functional groups have also been reported and used in postpolymerization Huisgen cycloaddition reactions. Gungor et reported an alkyne-functionalized... 

Tetramethylpiperidine-l-oxy (TEMPO)-containing alkoxyamine derivatives are widely used as unimolecular initiators for living radical polymerization [5], The key step of the presently accepted mechanism of polymerization is the reversible capping of the polymer chain by the nitroxide radical. In 2002, Otsuka and Takahara applied the reversible... 

Since TEMPO is only a regulator, not an initiator, radicals must be generated from another source the required amount of TEMPO depends on the initiator efficiency. Application of alkoxyamines (i.e., unimolecular initiators) allows for stoichiometric amounts of the initiating and mediating species to be incorporated and enables the use of multifunctional initiators, growing chains in several directions [61]. Numerous advances have been made in both the synthesis of different types of unimolecular initiators (alkoxyamines) that can be used not only for the polymerization of St-based monomers, but other monomers as well [62-69]. Most recently, the use of more reactive alkoxyamines and less reactive nitroxides has expanded the range of polymerizable monomers to acrylates, dienes, and acrylamides [70-73]. An important issue is the stability of nitroxides and other stable radicals. Apparently, slow self-destruction of the PRE helps control the polymerization [39]. Specific details about use of stable free radicals for the synthesis of copolymers can be found in later sections. 

Development of unimolecular initiators based on alkoxyamines allowed for better control over molecular weight and architecture, as well as expanded the library of monomers that could be polymerized by Due... 

Figure 5.7 Examples of alkoxyamines used as unimolecular initiator in nitroxide-mediated living radical polymerisation.

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