Nitroxide-mediated polymerization

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The nitroxide-mediated polymerization ( English nitroxide-mediated polymerization , NMP ) is a type of controlled radical polymerization . This is based on the fact that nitroxides (aminoxyl radicals) can react reversibly with the active chain end to form a so-called sleeping species. The balance between active and inactive chain ends is strongly on the side of the sleeping species, which means that the concentration of active species is very low. The probability that two active chains will meet and break off is thus minimized.

2,2,6,6-Tetramethylpiperidinyloxyl (TEMPO) is a radical that is too stable to attack monomers . However, it can react reversibly to the sleeping species with other radicals.

The method was developed in the 1970s at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia in the group of David Henry Solomon . Ezio Rizzardo was also involved .

example

If one looks at a sequence of the polystyrene , the chain end is reversibly linked to the species TEMPO. At 80 ° C the following equilibrium exists:

Reaction equation

If there is a polystyrene chain with a reactive end, this can continue to react normally with a chain growth reaction. However, if this is reversibly linked to TEMPO, the reaction is idle.

Web links

  • Ludger Tebben, Armido Studer: Nitroxides: Applications in synthesis and in polymer chemistry. In: Angewandte Chemie. 123, 2011, pp. 5138-5174, doi : 10.1002 / anie.201002547 .