Mechanism of Rate Enhancement Using Organic Acids in Nitroxide-Mediated Living Free-Radical Polymerizations

Veregin, Richard P. N.; Odell, Peter G.; Michalak, Lora M.; Georges, Michaël K.

doi:10.1021/ma951779d

Cited by 91 publications

(74 citation statements)

References 19 publications

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“…Because free-radical styrene polymerization in the absence of nitroxide is not affected by the addition of CSA, it was deduced that CSA interacts with the nitroxide. Georges and coworkers 148,149 found that the addition of CSA increases the consumption of TEMPO during the polymerization. A number of groups have used CSA to increase polymerization rates, 150,151 although no mechanism has been offered.…”

Section: Scheme 4 Schemementioning

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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Section: Scheme 4 Schemementioning

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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“…In this sense, as the amount of CSA increases, an increase in the polymerization rate and in the PDI values is observed as a result of disproportionation reactions that can undergo the nitroxide in the presence of CSA. 13 This situation shifts the equilibrium between the dormant and the active species to the latter and thus the control over the polymerization is lost. In the same way, the time required to reach the equilibrium differs from one reaction to another, being increased as the ratio of CSA/DEKTP is decreased.…”

Section: Effect Of the Dektp Concentrationmentioning

confidence: 99%

“…11 It has been pointed out that CSA increases the polymerization rate in NMRP while broadening the molecular weight distribution 12 ; this effect was attributed to nitroxide consumption as a result of nitroxide disproportionation by the acid molecule, which shifts the equilibrium to the formation of active radicals. 13 In addition, CSA can react with a nitroxide molecule to form hydroxylamine, leading to a poor control over the polymerization and in consequence broadening the molecular weight distribution. This effect is due to fewer TEMPO molecules present during the polymerization, which shifts the equilibrium to the active species.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of polystyrene oligomers by nitroxide‐mediated radical polymerization using diethylketone triperoxide as a multifunctional radical initiator

Anda

Santos

Morales

2011

J of Applied Polymer Sci

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Styrene oligomers (M n , 2500-3000 g/mol) with low polydispersity index and containing peroxidic groups within their structure were synthesized using a novel trifunctional cyclic radical initiator, diethylketone triperoxide (DEKTP), through nitroxide-mediated radical polymerization (NMRP), using OH-TEMPO. During the synthesis of the polystyrene (PS) oligomers, camphorsulfonic acid (CSA) was used to inhibit the thermal autoinitiation of styrene at the evaluated temperatures (T ¼ 120-130 C). The polymerization rate, which can be related to the slope of the plot of monomer conversion with reaction time, was monitored as a function of OH-TEMPO, DEKTP, and CSA concentrations. The experimental results showed that all the synthesized polymers presented narrow molecular weight distributions, and the monomer conversion and the molecular weight of the polymers increased as a function of reaction time.

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“…13 C APT, DEPT, and SSLR INEPT spectra were measured with the same number of points and with the evolution delays 7.35, 3.86, and 25 ms, respectively.…”

Section: H-and 13mentioning

confidence: 99%

Copolymerization and addition of styrene andN-phenylmaleimide in the presence of nitroxide

Lokaj¹,

Holler²,

K?�?³

2000

J. Appl. Polym. Sci.

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ABSTRACT:The copolymerization and addition reaction of styrene (S) with N-phenylmaleimide (PMI), either neat or in xylene, have been found to proceed at 125°C in the presence of 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) radicals. TEMPO-terminated alternating S-PMI copolymers and comonomer adducts were obtained. The amounts of the low molecular weight compounds increased with the increasing content of PMI in the initial mixture. The reaction suggests formation of monofunctional unimolecular initiators. In the autopolymerization of neat comonomers, a mediating role of TEMPO was observed. The synthesized copolymers containing TEMPO end groups were used as macroinitiators to initiate polymerization of styrene. The molecular weight distributions of resulting poly(styrene-alt-N-phenylmaleimide)-block-polystyrene copolymers indicated the presence of both low molecular weight termination products and some copolymer precursor. The copolymers and comonomer adducts were characterized using the nitrogen analysis, size-exclusion chromatography (SEC), and NMR spectroscopy.

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Mechanism of Rate Enhancement Using Organic Acids in Nitroxide-Mediated Living Free-Radical Polymerizations

Cited by 91 publications

References 19 publications

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

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

Synthesis of polystyrene oligomers by nitroxide‐mediated radical polymerization using diethylketone triperoxide as a multifunctional radical initiator

Copolymerization and addition of styrene andN-phenylmaleimide in the presence of nitroxide

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