Factors Influencing the C−O−Bond Homolysis of Trialkylhydroxylamines

Marque, Sylvain R. A.; Mercier, Christophe Le; Tordo, Paul; Fischer, Hanns

doi:10.1021/ma9918452

Cited by 256 publications

(398 citation statements)

References 59 publications

(81 reference statements)

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“…SG1-base initiators such as BlocBuilder have lower activation energy and much higher dissociation rate constant (k d ) compared to TEMPO-based initiators [45]. Additionally, Dire et al [46] confirmed that the rate constant for β-hydrogen transfer (k βtr ) of methyl methacrylate/SG1 system was three orders of magnitude lower compared to a n-butyl methacrylate/TEMPO system.…”

Section: Level Of Control Of the Copolymerizations And The Livingnessmentioning

confidence: 99%

Synthesis of Stimuli-responsive, Water-soluble Poly[2-(dimethylamino)ethyl methacrylate/styrene] Statistical Copolymers by Nitroxide Mediated Polymerization

Zhang

Marić

2011

Polymers

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Abstract:2-(Dimethylamino)ethyl methacrylate/styrene statistical copolymers (poly(DMAEMA-stat-styrene)) with feed compositions f DMAEMA = 80-95 mol%, (number average molecular weights M n = 9.5-11.2 kg mol −1 ) were synthesized using succinimidyl ester-functionalized BlocBuilder alkoxyamine initiator at 80 °C in bulk. Polymerization rate increased three-fold on increasing f DMAEMA = 80 to 95 mol%. Linear M n increases with conversion were observed up to about 50% conversion and obtained copolymers possessed monomodal, relatively narrow molecular weight distributions (polydispersity = 1.32-1.59).Copolymers with f DMAEMA = 80 and 90 mol% were also cleanly chain-extended with DMAEMA/styrene mixtures of 95 and 90 mol% DMAEMA, respectively, confirming the livingness of the copolymers. Copolymer phase behavior in aqueous solutions was examined by dynamic light scattering and UV-Vis spectroscopy. All copolymers exhibited lower critical solution temperature (LCST)-type behavior. LCST decreased with increasing styrene content in the copolymer and with increasing solution concentration. All copolymers were completely water-soluble and temperature insensitive at pH 4 but were more hydrophobic at pH 10, particularly copolymers with f DMAEMA = 80 and 85 mol%, which were water-insoluble. At pH 10, LCST of copolymers with f DMAEMA = 90 and 95 mol% were more than 10 °C lower compared to their solutions in neutral, de-ionized water. Block copolymers with two statistical blocks with different DMAEMA compositions exhibited a OPEN ACCESSPolymers 2011, 3 1399 single LCST, suggesting the block segments were not distinct enough to exhibit separate LCSTs in water.

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Section: Level Of Control Of the Copolymerizations And The Livingnessmentioning

confidence: 99%

Synthesis of Stimuli-responsive, Water-soluble Poly[2-(dimethylamino)ethyl methacrylate/styrene] Statistical Copolymers by Nitroxide Mediated Polymerization

Zhang

Marić

2011

Polymers

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“…In designing nitroxides for applications in NMP, much attention has been directed toward fine-tuning the nitroxide structure to lower the bond dissociation energy (BDE) of the transient Nalkoxyamines formed during the polymerization process, with the goal of running NMP at temperatures above room temperature but low enough to be compatible with complex functionality and to allow convenient industrial preparation. A number of elegant studies [52][53][54][55][56][57][58][59] have investigated the details of the kinetics of N-alkoxyamine thermal homolysis (k dissociation ) and recombination (k combination ) as it applies to NMP. In addition to kinetic considerations, the stability of the free nitroxide under the polymerization conditions is also critical.…”

Section: Introductionmentioning

confidence: 99%

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

Nilsen

Braslau

2005

J. Polym. Sci. A Polym. Chem.

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ABSTRACT:Nitroxides bearing an a-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.

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“…Very significant differences in polymerization rate and control are observed in scCO 2 between SG1-alkoxyamine 1d and TIPNOalkoxyamine 1a with M n (1d) > M n (1a) and higher polydispersities for 1d than 1a (1d: M w /M n = 1.25-1.57 and 1a: M w /M n = 1.22-1.36). The higher rate and inferior control for SG1 in scCO 2 is due to a combination of higher K, 50,51 and a higher solubility of SG1 in scCO 2 , leading to greater nitroxide partitioning away from the locus of polymerization after particle formation. Although there is no literature data available for nitroxide solubilities in scCO 2 , one may expect a greater solubility for TIPNO in the organic phase (particles) due to TIPNO's organic nature in comparison to SG1, which contains heteroatoms (e.g.…”

Section: Precipitation Polymerizations In Supercritical Carbon Dioxidmentioning

confidence: 99%

Synthesis of fluorinated alkoxyamines and alkoxyamine-initiated nitroxide-mediated precipitation polymerizations of styrene in supercritical carbon dioxide

et al. 2014

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was found to give reasonably controlled/living nitroxide-mediated (NMP) precipitation polymerizations of styrene in supercritical carbon dioxide (scCO 2 ). In contrast under the same conditions, the analogous SG1 (N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide)-alkoxyamine gave higher rates of polymerization and inferior controlled/living character. The circumvention of the requirement for excess free [nitroxide] 0 allowed the study of nitroxide partitioning effects in scCO 2 for three newly synthesized fluorinated alkoxyamines. Two alkoxyamines dissociated into scCO 2 -philic fluorinated TIPNO-nitroxide derivatives, while another contains a similar sized fluorinated "foot". Despite the increase steric bulk about the N-O bond for the novel fluorinated alkoxyamines, all polymerizations proceeded at a similar rate and level of control to the TIPNO system in solution (toluene). PREDICI simulations for the styrene/TIPNO system are used to support extensive partitioning effects observed in scCO 2 for the fluorinated alkoxyamines. IntroductionSupercritical carbon dioxide (scCO 2 ) is a benign solvent used to circumvent the requirement for environmentally damaging volatile organic solvents. [1][2][3] Advantages include a readily accessible critical point (31 °C and 7.4 MPa), 4 variable solubility by subtle changes in pressure and temperature, 5 and the lack of chain transfer to solvent in radical polymerizations. 6,7 It is particularly well-suited for heterogeneous radical polymerizations, since reagents such as the monomer, initiator and controlling agent are generally soluble in scCO 2 , but the resultant polymer is insoluble and precipitates. 2,3 If the precipitation system is carried out in the presence of a colloidal stabilizer to prevent coagulation of particles, then dispersion polymerization results giving polymer of narrow particle size distributions and well-defined particles (d ≈ 100 nm to 15 μm). 1-3The monomer is not always soluble in the reaction medium, such as in the controlled/living nitroxide-mediated radical polymerization (NMP) of N-isopropylacrylamide (NIPAM) in scCO 2 , where an inverse suspension system is generated. 8,9 In recent years, there has been a proliferation in the numbers of reported controlled/living precipitation and dispersion polymerizations in scCO 2 with NMP, [9][10][11][12][13][14][15][16][17][18][19][20][21] atom transfer radical polymerization (ATRP), 22-29 reversible addition-fragmentation chain transfer (RAFT) 3, 30-39 and iodine transfer polymerization (ITP). 40,41 The slow build up in molecular weight (MW) in a controlled/living system by virtue of the equilibrium between active propagating radicals and dormant polymer chains allows measurement of the critical degree of polymerization (J crit ) before polymer chains precipitate from solution or the continuous phase (containing monomer and scCO 2 ). After J crit , the polymerization continues in the monomer-rich particle phase. For controlled/living precipitation/dispersion polymerizations, J crit can be ...

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Factors Influencing the C−O−Bond Homolysis of Trialkylhydroxylamines

Cited by 256 publications

References 59 publications

Synthesis of Stimuli-responsive, Water-soluble Poly[2-(dimethylamino)ethyl methacrylate/styrene] Statistical Copolymers by Nitroxide Mediated Polymerization

Synthesis of Stimuli-responsive, Water-soluble Poly[2-(dimethylamino)ethyl methacrylate/styrene] Statistical Copolymers by Nitroxide Mediated Polymerization

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

Synthesis of fluorinated alkoxyamines and alkoxyamine-initiated nitroxide-mediated precipitation polymerizations of styrene in supercritical carbon dioxide

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