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Monday, August 15, 2005

Free-Radical Polymerization: Alkoxyamine Initiators



Polymers have important uses in both research and industry. Alkoxyamines are used in ATRP (atom transfer radical polymerization)-based polymerizations and can serve as efficient regulators in the preparation of polymers. In the past, the alkoxyamines were produced by the creation of radicals that are carbon-centered and were then trapped by nitroxide. This method, however, gave low yields and undesired byproducts. The reaction shown here takes place at low temperatures and in the presence of a nitroxide, utilizing an ATRP-based initiator that is treated with copper bromide. The ATRP is involved in the living radical polymerization system. Me6-tren ligand forms a catalyst complex for the reaction of the initiator with nitroxide. Equilibrium between the transfer to and from radicals and dormant species in the reaction is controlled by the Me6-tren ligand forming a complex with the Cu(II), which the free radicals can then interact with. The catalyst name Me6-tren stands for the chemical tris(2-(dimethylamino)ethyl)-amine. This is a more effective procedure for preparation that results in high yields. Discoveries such as this are important in areas such as nanotechnology.

Here is the CiteULike article.

Here are articles about the Me6-tren ligand and its naming.

This source discusses the use of alkoxyamines in free-radical polymerization.

5 Comments:

  • 1) What is the role of alkoxyamines for polymers?
    2) Where did you get the point you make that Me6-tren forms a complex?
    3) Define all abbreviations like tren

    By Blogger Jean-Claude Bradley, at 10:23 AM  

  • 1) Make sure to include the parentheses at the right places for the name of Me6-TREN. Just like in math, without parentheses it doesn't make sense.
    2) The Me6-TREN is a polyamine. What do you think it complexes with?

    By Blogger Jean-Claude Bradley, at 6:29 PM  

  • The article you cite has the correct name of the polyamine. Read it carefully and think about what you are writing.

    By Blogger Jean-Claude Bradley, at 6:58 AM  

  • Full marks. This was a very ambitious choice of reaction based on the chemistry we covered so far but I think you finally have detailed the key points. Just make sure to fix that the name you gave was for Me6TREN, not TREN.

    By Blogger Jean-Claude Bradley, at 1:21 PM  

  • "Alkoxyamines are used in ATRP (atom transfer radical polymerization)-based polymerizations and can serve as efficient regulators in the preparation of polymers."
    This is wrong. Alkoxyamines are used in NMP (Nitroxide-Mediated Polymerization) and not in ATRP. The precursor you are using (the bromo-functionalized molecule) is a species used in ATRP as an initiator.
    The two mechanisms are different. NMP is based on a thermal equilibrium between alkoxyamines on one hand and free nitroxides and free radicals on the other side. ATRP is based on a redox equilibrium mediated by a transition metal complex (for example CuX/bipyridine) able to cleave the C-X bond.

    By Anonymous Guillaume Delaittre, at 12:06 PM  

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