Synthesis and evaluation of sterically hindered 1,1-diamantyl nitroxide as a low-temperature mediator for the stable free radical polymerization process
[en] An efficient procedure for the oxidation of 1,1-diadamantylamine with m-chloroperbenzoic acid (m-CPBA) to the corresponding sterically hindered nitroxide in high yield (72%) is reported. The corresponding styrene-based alkoxyamine was synthesized by an atom transfer radical addition (ATRA) reaction. Because of the bulkiness of the adamantyl substituents, the cleavage of the C−ON bond of the alkoxyamine occurred readily at temperatures below 100 °C. However, in spite of the low bond dissociation temperature of the alkoxyamine, the (co)polymerizations of styrene and n-butyl acrylate proceeded poorly. The results in this paper support the argument that the most important determinant in a nitroxide-mediated polymerization of styrene and acrylate is the ability to control the excess concentration of nitroxide in solution either by an inherent instability of the nitroxide or by the use of additives that destroy the excess nitroxide. Thus, for the 1,1-diadamantyl nitroxide case, and maybe more generally, while a lower C−O bond dissociation energy of an alkoxyamine moiety at the end of the chain may allow lower polymerization temperatures and faster reactions rates, it does not enable polymerizations to proceed to high conversions if the excess nitroxide is not controlled in some manner.
Disciplines :
Chemistry
Author, co-author :
Debuigne, Antoine ; University of Toronto at Mississauga, Canada > Department of Chemical and Physical Sciences
Chan-Seng, Delphine; University of Toronto at Mississauga, Canada > Department of Chemical and Physical Sciences
Li, Lichun; University of Toronto at Mississauga, Canada > Department of Chemical and Physical Sciences
Hamer, Gordon K.; University of Toronto at Mississauga, Canada > Department of Chemical and Physical Sciences
Georges, Michael K.; University of Toronto at Mississauga, Canada > Department of Chemical and Physical Sciences
Language :
English
Title :
Synthesis and evaluation of sterically hindered 1,1-diamantyl nitroxide as a low-temperature mediator for the stable free radical polymerization process
Publication date :
21 August 2007
Journal title :
Macromolecules
ISSN :
0024-9297
eISSN :
1520-5835
Publisher :
American Chemical Society, Washington, United States - District of Columbia
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