Nitroxide mediated radical polymerization

Nitroxide -mediated polymerization ( nitroxide -mediated polymerization English, NMP ) is a type of controlled radical polymerization. This is due to the fact that nitroxides can react reversibly to a so-called dormant species with the active chain end. The balance between active and inactive end of the chain is strongly on the side of the dormant species, thereby increasing the concentration of active species is very low. The likelihood that meet two active chains and abort is thus minimized.

2,2,6,6- tetramethylpiperidinyloxyl (TEMPO ), is a radical which is stable to attack monomers. However, it can react with other radicals reversibly to the dormant species.

The procedure was developed in the 1970s at the CSIRO in Australia in the group of David Solomon. Participation was also Ezio Rizzardo.

Example

Considering a sequence of the polystyrene, the end of the chain is connected to the reversible dormant species TEMPO.

At 80 ° C the following equilibrium exists:

If there is a polystyrene chain with reactive end, this can normally react further chain growth reaction.

Is this, however, reversibly connected with the dormant species, rests the reaction.