Nitrogen-Centered Radical Mediated Polymerization

A few studies have appeared on systems based on persistent nitrogen-centered radicals. Yamada et examined the synthesis of block polymers of S and MMA initiated by derivatives of the triphenylverdazyl radical 115. Klapper and coworkers have reported on the use of triazolinyl radicals [e.g. 116 and 117). The triazolinyl radicals have been used to control S, methacrylate and acrydatc polymerization and for the synthesis of block copolymers based on these monomers tBA, MMA, - - BMA, DMAEMA, TMSEMA,  

Reaction conditions in these experiments were similar to those used for NMP. The triazolinyl radicals show no tendency to give disproportionation with methacrylate propagating radicals. Di.spcrsitics reported arc typically in the range 

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Most polymerizations in this section can be categorized as stable (free) radical-mediated polymerizations (sometimes abbreviated as SFRMP). In the following discussion systems have been classed according to the type of stable radical involved, which usually correlates with the type of bond homolyzed in the activation process. Those described include systems where the stable radical is a sulfur-ccntcrcd radical (Section 9.3.2), a scicnium-ccntcrcd radical (Section 9.3.3), a carbon-centered radical (Sections 9.3.4 and 9.3.5), an oxygen-centered radical (Sections 9.3.6, 9.3.7), or a nitrogen-centered radical (Section 9.3.8). Wc also consider polymerization mediated by cobalt complexes (Section 9.3.9) and certain monomers (Section 9.3.5). 

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