New 7‐membered diazepanone alkoxyamines for nitroxide‐mediated radical polymerization

Nesvadba, Peter; Bugnon, Lucienne; Sift, Rosemarie

doi:10.1002/pola.20200

Cited by 24 publications

(27 citation statements)

References 51 publications

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“…In the last few years, nitroxide‐mediated living radical polymerization has been widely used in the synthesis of controlled macromolecular structures 1–6. Also, previous limitations of this technique, such as slow reactions or poor control, have been successfully addressed and overcome to various extents by different authors 7–11. Because of its practical implications, considerable attention has been given to the mechanism and kinetics of the nitroxide‐mediated polymeri zation (NMP) of styrene,12–21 and a fair grasp of its general features seems to be well established, despite a still incomplete understanding of the mechanism of thermal styrene autoinitiation.…”

Section: Introductionmentioning

confidence: 99%

Incubation period in the 2,2,4,4‐tetramethyl‐1‐piperidinyloxy‐mediated thermal autopolymerization of styrene: Kinetics and simulations

Saldívar‐Guerra

Bonilla

Zacahua³

et al. 2006

J. Polym. Sci. A Polym. Chem.

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Mechanisms and simulations of the induction period and the initial polymerization stages in the nitroxide‐mediated autopolymerization of styrene are discussed. At 120–125 °C and moderate 2,2,4,4‐tetramethyl‐1‐piperidinyloxy (TEMPO) concentrations (0.02–0.08 M), the main source of radicals is the hydrogen abstraction of the Mayo dimer by TEMPO [with the kinetic constant of hydrogen abstraction (kh)]. At higher TEMPO concentrations ([N•] > 0.1 M), this reaction is still dominant, but radical generation by the direct attack against styrene by TEMPO, with kinetic constant of addition kad, also becomes relevant. From previous experimental data and simulations, initial estimates of kh ≈ 1 and kad ≈ 6 × 10−7 L mol−1 s−1 are obtained at 125 °C. From the induction period to the polymerization regime, there is an abrupt change in the dominant mechanism generating radicals because of the sudden decrease in the nitroxide radicals. Under induction‐period conditions, the simulations confirm the validity of the quasi‐steady‐state assumption (QSSA) for the Mayo dimer in this regime; however, after the induction period, the QSSA for the dimer is not valid, and this brings into question the scientific basis of the well‐known expression kth[M]3 (where [M] is the monomer concentration and kth is the kinetic constant of autoinitiation) for the autoinitiation rate in styrene polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6962‐6979, 2006

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Section: Introductionmentioning

confidence: 99%

Incubation period in the 2,2,4,4‐tetramethyl‐1‐piperidinyloxy‐mediated thermal autopolymerization of styrene: Kinetics and simulations

Saldívar‐Guerra

Bonilla

Zacahua³

et al. 2006

J. Polym. Sci. A Polym. Chem.

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“…Experimental. -The synthesis and the properties of nitroxide radicals 11 [26], 12 [27], and 14 and 15 [28] have been described elsewhere. The radicals were analytically pure.…”

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confidence: 99%

Re‐formation Reaction of Cyclic Nitroxide‐Based Alkoxyamines: Steric and Polar/Stabilization Effects

Fischer

Marque²,

Nesvadba

2006

Helvetica Chimica Acta

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Dedicated to Professor Hanns Fischer for his invaluable contribution in the fields of nitroxide-mediated polymerization and radical chemistryIn nitroxide-mediated radical polymerization, the polymerization times decrease with the increasing re-formation rate constant of the CÀON bond (! alkoxyamine) between the growing polymer chain and the nitroxide radical. The factors influencing the re-formation rate constant are of considerable interest, but up to now, the polar/stabilization effects have not been addressed thoroughly. The combination of new data with previously reported data now showed that the re-formation rate constant k c increases with the increasing polar character of the substituents attached to the nitroxide moiety. The polar/stabilization effects are weaker for the re-formation than for the homolysis of the CÀON bond, and may be mainly attributed to the relocation of the odd electron onto the O-atom of the NÀO moiety, i.e., the stabilization of the nitroxide moiety. Hence, it is possible to predict the values of k c by combining both the polar/stabilization (s I ) and steric effects (E , nitroxide-mediated radical polymerization (NMP) has often been used for the synthesis of living polymers and copolymers with narrow polydispersities and controlled molecular masses and architecture [4 -6]. The mechanism of NMP outlined in Scheme 1 involves the cleavage of capped chain molecules (dormant species) into propagating alkyl and persistent nitroxide radicals (k d ). The propagating radicals grow by monomer addition (k p ) and form longer dormant chains by cross-coupling with the nitroxide radicals (k c ). Simultaneously, the usual self-termination (k t ) of the propagating radicals into unreactive polymer products takes place. This removes the propagating radicals and increases the concentration of nitroxide radicals over time; the cross-coupling reaction (k c ), therefore, dominates over self-termination [7] [8]. For an extended time range, a quasi-equilibrium of the reversible cleavage exists which is characterized by weakly time-dependent radical concentrations and a large excess of the persistent radicals over the propagating radicals.For the well-controlled and living radical polymerization of a given monomer with propagation and termination rate constants k p and k t , the rate constants of the reversible cleavage k d and k c must fall into proper ranges [7 -9]. In general, one aims at rela-

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“…To begin with, several sterically hindered alkoxyamines were prepared [23][24][25][26]. Typical examples are shown in Fig.…”

Section: Industrial Realization Of Living Radical Polymerizationmentioning

confidence: 99%

Effects to Improve the Quality of Life: Color, Performance and Protection from Ciba Specialty Chemicals

Rutsch¹,

Čech²

2007

Chimia

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Ciba Specialty Chemicals creates effects to improve the quality of life. Building on its technical competencies, the company has developed major innovative product groups that provide color, performance and protection. Antioxidants and light stabilizers protect plastics, coatings, photographic pictures and wood from degradation induced by sunlight, air, ozone, heat, fire and mechanical stress. UV absorbers protect human skin from sunburn and photo-induced ageing. Pigments and dyes add beautiful colors to objects of everyday life, serve as recording media for optical information storage on digital versatile discs (DVDs) and are used as color filters in liquid crystal displays (LCDs). Effect pigments allow creation of color and visual effects by interference. Polymeric flocculants are essential components for solid–liquid separation processes in wastewater treatment and paper production. Photolatent catalysts are key components for light-induced polymerization reactions. New sterically hindered N-alkoxyamines are initiators for nitroxide mediated radical polymerization (NMP) reactions leading to new pigment dispersants with well-defined molecular weights and narrow molecular weight distribution. New N-acyloxyamines are proposed as peroxide substitutes for controlled degradation of high molecular weight polypropylene. A new clarifier can be used to produce polypropylene with enhanced transparency and excellent mechanical properties. Progress in enabling sciences such as nanotechnology and biotechnology together with new technologies entering the markets will offer outstanding opportunities for new developments in specialty chemicals.

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New 7‐membered diazepanone alkoxyamines for nitroxide‐mediated radical polymerization

Cited by 24 publications

References 51 publications

Incubation period in the 2,2,4,4‐tetramethyl‐1‐piperidinyloxy‐mediated thermal autopolymerization of styrene: Kinetics and simulations

Incubation period in the 2,2,4,4‐tetramethyl‐1‐piperidinyloxy‐mediated thermal autopolymerization of styrene: Kinetics and simulations

Re‐formation Reaction of Cyclic Nitroxide‐Based Alkoxyamines: Steric and Polar/Stabilization Effects

Effects to Improve the Quality of Life: Color, Performance and Protection from Ciba Specialty Chemicals

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