General Features of Atom Transfer Radical Polymerization ATRP

General Features of Atom Transfer Radical Polymerization (ATRP) 

Radical polymerizations can be controlled by addition of a suitable metal complex, which reversibly transforms the free radicals into a dormant species. Such is the case in atom transfer radical polymerization (ATRP) [155, 156]. Contrary to the 

due to radical termination, an excess of metal halide is present and radicals are more likely to react back to the dormant form than to terminate (persistent radical effect) [158, 159]. Under these conditions, a metal-catalyzed equilibrium between dormant and achve chains is estabhshed and the reaction is controlled the average molecular weight grows linearly with conversion and the poly-dispersity remains close to 1. The tradeoff in return for achieving polymer molecular weight control is a slow polymerizahon rate, which is characteristic for ATRP. 

The kinetics are dependent on the nature of the metal complex and also on the relative amount of initiator. Usually, the organic hahde used as an initiator and the metal compound are employed in a 1 1 molar raho as control of molecular weight is ophmal under these conditions, but higher ratios can also be used [155]. The metal compound is thus effechve in catalytic amounts . It should be noted that by contrast to, for instance, olefin polymerization the metal complexes involved in ATRP are not directly part of the polymerizahon chain growth cycle. Nonetheless, fhey are usually designated as catalysts in the hterature, and fhis des-ignahon is adopted throughout this sechon. 

3 Controlled Free-Radical PolYmerization in Aqueous Systems with Metai Complexes 

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