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New polymer synthesis by nitroxide mediated living radical polymerizations.

Controlled/living radical polymerization: Features, developments, and perspectives

Keywords: Fragmentation Chain-Transfer ; Self-Assembled Monolayers ; Walled Carbon Nanotubes ; Well-Defined Polymer ; Nitroxide-Mediated Polymerization ; Block-Copolymer Brushes ; Poly(Methyl Methacrylate) Brushes ; Transfer Raft Polymerization ; Quartz-Crystal Microbalance ; Poly(Acrylic Acid) Brushes Reference EPFL-REVIEW-148464doi:10.1021/cr900045aView record in Web of Science Record created on 2010-04-23, modified on 2017-05-10

Polymer Brushes via Surface-Initiated Controlled Radical Polymerization: Synthesis, Characterization, Properties, and Applications

Polymer brushes: surface-immobilized macromolecules

Examination of novel alkoxyamines has demonstrated the pivotal role that the nitroxide plays in mediating the “living” or controlled polymerization of a wide range of vinyl monomers. Surveying a variety of different alkoxyamine structures led to α-hydrido derivatives based on a 2,2,5-trimethyl-4-phenyl-3-azahexane-3-oxy, 1, skeleton which were able to control the polymerization of styrene, acrylate, acrylamide, and acrylonitrile based monomers. For each monomer set, the molecular weight could be controlled from 1000 to 200 000 amu with polydispersities typically 1.05−1.15. Block and random copolymers based on combinations of the above monomers could also be prepared with similar control. In comparison with 2,2,6,6-tetramethylpiperidinoxy (TEMPO), these new systems represent a dramatic increase in the range of monomers that can be polymerized under controlled conditions and overcome many of the limitations associated with nitroxide-mediated “living” free radical procedures. Monomer selection and functional...

Development of a Universal Alkoxyamine for “Living” Free Radical Polymerizations

Tetra-n-butylammonium oxone. Oxidations under anhydrous conditions

Nitroxides bearing an α-hydrogen decompose upon heating in a bimolecular reaction. A new mechanism is proposed for the decomposition of t-butylisopropylphenyl nitroxide (TIPNO) involving the formation of a head-to-tail dimer, single electron transfer to form an oxammonium salt, epimerization to the corresponding nitrone, and elimination to form a conjugated oxime. This mechanism may provide insights into designing new nitroxides for use in controlled polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 697–717, 2006

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pola.21207

Nitroxide decomposition: Implications toward nitroxide design for applications in living free-radical polymerization

Quantum dot (QD) fluorescence is effectively quenched at low concentration by nitroxides bearing amine or carboxylic acid ligands. The association constants and fluorescence quenching of CdSe QDs with these derivatized nitroxides have been examined using electron paramagnetic resonance (EPR) and fluorescence spectroscopy. The EPR spectra in the nonprotic solvent toluene are extremely sensitive to intermolecular and intramolecular hydrogen bonding of the functionalized nitroxides. Fluorescence measurements show that quenching of QD luminescence is nonlinear, with a strong dependence on the distance between the radical and the QD. The quenched fluorescence is restored when the surface-bound nitroxides are converted to hydroxylamines by mild reducing agents or trapped by carbon radicals to form alkoxyamines. EPR studies indicate that photoreduction of the nitroxide occurs in toluene solution upon photoexcitation at 365 nm. However, photolysis in benzene solution gives no photoreduction, suggesting that photo...

Distance-Dependent Fluorescence Quenching and Binding of CdSe Quantum Dots by Functionalized Nitroxide Radicals

Low-temperature methods for the preparation of monomeric initiators for use in “living” free radical olefin polymerizations have been developed. Oxidative methods for generating carbon radicals in the presence of nitroxide traps such as TEMPO utilize PbO2 with benzylic, alkyl, or phenylhydrazines or CuCl2 with lithium enolates. Photolytic methods employ [Cp(CO)2Fe]2 with a benzylic bromide, diphenyl disulfide with styrene, or di-tert-butyl peroxide with ethers. The use of di-tert-butyl hyponitrite with ethers generates carbon radicals at 50 °C that are trapped by TEMPO.

Rebecca Braslau

Papers

Development of a Universal Alkoxyamine for “Living” Free Radical Polymerizations

Tetra-n-butylammonium oxone. Oxidations under anhydrous conditions

Nitroxide decomposition: Implications toward nitroxide design for applications in living free-radical polymerization

Distance-Dependent Fluorescence Quenching and Binding of CdSe Quantum Dots by Functionalized Nitroxide Radicals

Low-temperature preparations of unimolecular nitroxide initiators for living free radical polymerizations