3.10 - Nitroxide-Mediated Polymerization

Kinetics of Living Radical Polymerization

In the present short review article recent achievements in nitroxide-mediated radical polymerizations are presented. The basic concept behind these reactions, which is the Persistent Radical Effect (PRE), will be briefly explained. The effect of the nitroxide structure on the polymerization process will be discussed. Moreover, results of nitroxide-mediated radical polymerizations in aqueous dispersions will be summarized. Finally, applications of the PRE to environmentally benign radical chemistry such as nitroxide-mediated alkoxyamine isomerization and carboaminoxylation reactions are presented. Moreover, the potential use of microwave-induced heating to conduct these thermal radical reactions will be discussed.

Nitroxide‐mediated radical processes

In nitroxide-mediated polymerization, NMP, the role of the initiation and therefore the role of the initiating dissociation rate constant kd1 on the control and livingness of a styrene and n-butyl acrylate polymerization was investigated. Different polymerizations were carried out, initiated with two different alkoxyamines based on the same nitroxide (1• or SG1). Kinetic modeling studies using the PREDICI software are used to explain these results. The use of a new tertiary SG1-based alkoxyamine 1a instead of the secondary SG1-based alkoxyamine 1b improved the control of the polymerization of both styrene and n-butyl acrylate. In particular, the polymerization of n-butyl acrylate can be carried out without adding any extra initial amount of nitroxide and the controlled polymerization of styrene at 90 °C is now possible. The complete kinetic analysis showed that the main role of the alkoxyamine with a high dissociation rate constant is to produce quickly in situ an extra amount of free nitroxide, which is ...

Nitroxide-Mediated Polymerization: The Pivotal Role of the kd Value of the Initiating Alkoxyamine and the Importance of the Experimental Conditions

This review article describes the preparation of polymer brushes by nitroxide-mediated radical polymerization using either the 'grafting to' or the 'grafting from' approach. The use of TEMPO as a classical initiator is intensively described. More sophisticated nitroxides are also included in the discussion. Brush formation on flat surfaces such as wafers and also on particles is reported. Finally, some applications of polymer brushes are presented.

Jens Sobek

Papers

Steric Effects of Ring Substituents on the Decay and Reformation Kinetics of Piperazinone-Based Alkoxyamines