Nitroxide mediated polymerization using diphenyl azabutane N-oxides. A study of electronic effects and of the [nitroxide]/[initiator] ratio on the polymerization control

Cuatepotzo-Dı́az, Rubén; Albores‐Velasco, Martha; Saldívar‐Guerra, Enrique; Jiménez, Fabiola Becerril

doi:10.1016/j.polymer.2003.11.035

Cited by 16 publications

(11 citation statements)

References 41 publications

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“…(which was obtained from ethylbenzene and di-tert-butyl peroxyoxalate) following the procedure of Miura et al [21] The alkoxyamine obtained, a colorless oil, was characterized by IR and 1 H NMR spectroscopy. The synthesis of the nitrone is described elsewhere, [22] as well as the synthesis of the di-tertbutyl peroxyoxalate. [23] Polymerizations For each reaction alkoxyamine 1 (0.1989 and 1.8496 g for the reactions with 0.012 and 0.113 M concentrations of alkoxyamine, respectively) and styrene from Aldrich (50 mL) were mixed and distributed (5 mL) in 10 vials.…”

Section: Synthesis Of the Alkoxyaminementioning

confidence: 99%

On the Nitroxide Quasi‐Equilibrium in the Alkoxyamine‐Mediated Radical Polymerization of Styrene

Saldívar‐Guerra

Bonilla

Becerril

et al. 2006

Macro Theory & Simulations

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Summary: The range of validity of two popular versions of the nitroxide quasi‐equilibrium (NQE) approximation used in the theory of kinetics of alkoxyamine mediated styrene polymerization, are systematically tested by simulation comparing the approximate and exact solutions of the equations describing the system. The validity of the different versions of the NQE approximation is analyzed in terms of the relative magnitude of (dN/dt)/(dP/dt). The approximation with a rigorous NQE, kc[P][N] = kd[PN], where P, N and PN are living, nitroxide radicals and dormant species respectively, with kinetic constants kc and kd, is found valid only for small values of the equilibrium constant K (10−11–10−12 mol · L−1) and its validity is found to depend strongly of the value of K. On the other hand, the relaxed NQE approximation of Fischer and Fukuda, kc[P][N] = kd[PN]0 was found to be remarkably good up to values of K around 10−8 mol · L−1. This upper bound is numerically found to be 2–3 orders of magnitude smaller than the theoretical one given by Fischer. The relaxed NQE is a better one due to the fact that it never completely neglects dN/dt. It is found that the difference between these approximations lies essentially in the number of significant figures taken for the approximation; still this subtle difference results in dramatic changes in the predicted course of the reaction. Some results confirm previous findings, but a deeper understanding of the physico‐chemical phenomena and their mathematical representation and another viewpoint of the theory is offered. Additionally, experiments and simulations indicate that polymerization rate data alone are not reliable to estimate the value of K, as recently suggested.Validity of the rigorous nitroxide quasi‐equilibrium assumption as a function of the nitroxide equilibrium constant.imageValidity of the rigorous nitroxide quasi‐equilibrium assumption as a function of the nitroxide equilibrium constant.

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Section: Synthesis Of the Alkoxyaminementioning

confidence: 99%

On the Nitroxide Quasi‐Equilibrium in the Alkoxyamine‐Mediated Radical Polymerization of Styrene

Saldívar‐Guerra

Bonilla

Becerril

et al. 2006

Macro Theory & Simulations

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“…41 These polymerizations demonstrated good control with styrene monomers, but 45,56,[82][83][84][85][86][87] has allowed the extension of NMP to a much wider range of nonstyrenic olefin monomers. These a-hydrogen-bearing nitroxides are stable and easily handled at room temperature but do undergo bimolecular disproportionation under the thermal conditions of polymerization.…”

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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“…Many experimental3 but few theoretical3a, f–g, j–k, m–o, 5 studies have been performed to estimate factors influencing the BDE (NOC) of N ‐alkoxyamines. Experimental results show that narrow polydispersities and high polymerization rates depend on the ease of the NOC bond homolysis 3f.…”

Section: Introductionmentioning

confidence: 99%

Homolysis of N‐alkoxyamines: A Computational Study

2006

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During nitroxide-mediated polymerization (NMP) in the presence of a nitroxide R2(R1)NO*, the reversible formation of N-alkoxyamines [P-ON(R1)R2] reduces significantly the concentration of polymer radicals (P*) and their involvement in termination reactions. The control of the livingness and polydispersity of the resulting polymer depends strongly on the magnitude of the bond dissociation energy (BDE) of the C-ON(R1)R2 bond. In this study, theoretical BDEs of a large series of model N-alkoxyamines are calculated with the PM3 method. In order to provide a predictive tool, correlations between the calculated BDEs and the cleavage temperature (Tc), and the dissociation rate constant (k(d)), of the N-alkoxyamines are established. The homolytic cleavage of the N-OC bond is also investigated at the B3P86/6-311++G(d,p)//B3LYP/6-31G(d), level. Furthermore, a natural bond orbital analysis is carried out for some N-alkoxyamines with a O-C-ON(R1)R2 fragment, and the strengthening of their C-ON(R1)R2 bond is interpreted in terms of stabilizing anomeric interactions.

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Nitroxide mediated polymerization using diphenyl azabutane N-oxides. A study of electronic effects and of the [nitroxide]/[initiator] ratio on the polymerization control

Cited by 16 publications

References 41 publications

On the Nitroxide Quasi‐Equilibrium in the Alkoxyamine‐Mediated Radical Polymerization of Styrene

On the Nitroxide Quasi‐Equilibrium in the Alkoxyamine‐Mediated Radical Polymerization of Styrene

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

Homolysis of N‐alkoxyamines: A Computational Study

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