Transformation of sterically hindered amines (HALS) to nitroxyl radicals: What are the actual stabilizers?

Brede, O.; Göttinger, H. A.

doi:10.1002/(sici)1522-9505(19981201)261-262:1<45::aid-apmc45>3.0.co;2-w

Cited by 8 publications

(6 citation statements)

References 25 publications

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“…2a–c), where only negligible oxidation of SHA to nitroxide was found. These results are in accord with the previous investigations, in which to this reaction pathway of SHA oxidation less importance was attributed (44–46).…”

Section: Resultssupporting

confidence: 93%

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Barbieriková

Mihalíková

Brezová³

2012

Photochem & Photobiology

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The reactions of sterically hindered amines (SHA) were investigated in acetonitrile solutions and TiO(2) suspensions upon exposure to monochromatic radiation, λ=365 nm, by means of in situ EPR spectroscopy. The formation of singlet oxygen, as one of the possible oxidation agents for SHA, in these systems is affected significantly by solvent used and the experimental conditions. Experiments in homogeneous media evidenced alternative pathways for the SHA oxidation with a variety reactive oxygen species involved. In anhydrous acetonitrile solutions containing KO(2), the SHA oxidation was negligible not only in the dark but also on continuous exposure. However, the presence of water, even at low concentrations, led to the transformation of O(2)(•-) to singlet oxygen and hydrogen peroxide, which served as a source of hydroxyl radicals. These species participated in oxidation of SHA resulting in the generation of nitroxide radicals. To investigate the influence of different competitive reactions of SHA with other ROS formed upon TiO(2) photoexcitation, a series of experiments using different additives (e.g. KO(2), H(2)O(2), NaN(3), dimethylsulfoxide, methanol as organic cosolvents) under air or argon were performed. The detailed analysis of paramagnetic intermediates formed upon the irradiation of the studied systems was accomplished using EPR spin trapping technique.

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Section: Resultssupporting

confidence: 93%

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Barbieriková

Mihalíková

Brezová³

2012

Photochem & Photobiology

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“…The rate of BZ consumption in aerated PS matrix in the presence of TMP is slightly higher as in its absence. Chemical scavenging of alkylperoxy radicals and benzophenone triplet by HAS in their parent amine form is known 18. Analogically the triplet of BZ can react with TMP and increase the depletion of BZ in its presence.…”

Section: Resultsmentioning

confidence: 99%

“…The rate is lower than that in the case of BZ alone and, in studied range, it surprisingly decreases as NO concentration decreases. The quenching of the triplet state of ketones and aromatic hydrocarbons by nitroxides is known 18, 26. Full triplet quenching in solution is reached26 at 1‐oxo‐2,2,6,6‐tetramethylpiperidin concentration of 2–4 m M .…”

Section: Resultsmentioning

confidence: 99%

“…Their action is explained by the inhibition of photo‐ or thermooxidation of polymers. N‐oxyl radicals formed during HAS action were proved to be an active species,14, 15 but the details of the mechanism of their action are still not yet clear 16–18. To contribute to the understanding of the mechanism of action of HAS and at the same time to elucidate the mechanism of phototransformation of BZ groups in solid polymer matrix, the effect of unbounded or bounded HAS (Scheme ) is examined on photoperoxidation of BZ groups in polystyrene (PS) matrices.…”

Section: Introductionmentioning

confidence: 99%

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Antibacterial and biocompatible surfaces based on dopamine autooxidized silver nanoparticles

Sureshkumar

Siswanto

Chen

et al. 2012

J Polym Sci B Polym Phys

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A facile and green method is proposed to immobilize silver nanoparticles (AgNPs) showing antibacterial and biocompatible properties on surfaces of substrates. The adhesive and reductive polydopamine (Pdop) coating was applied on the substrates such as polyethylene, glass, poly(methyl methacrylate), and poly(lactic‐co‐glycolic acid) by simply dipping into dopamine solutions. AgNPs of 50–70 nm formed uniformly on the Pdop‐coated surfaces after immersing in silver nitrate solution where the density of AgNPs was modulated by Pdop immobilization time. Antibacterial efficacy, lactate dehydrogenase assay, and cell morphology observed by microscopy indicated that the as‐prepared AgNPs deposited on Pdop/substrates possessed effective biocidal properties and did not inhibit the growth of L‐929 cells mouse fibroblasts. The proposed method can be easily applied on different substrates and revealed good biocompatibility, which could be further developed for applications in biomaterials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013

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“…Depending on the neighborhood, these amine radical cations deprotonate via secondary amines under formation of aminyl radicals and towards tertiary amines under intermediate formation of a-aminoalkyl radicals, which are in the presence of oxygen transformed via different peroxy radical intermediates into nitroxyl radicals (Fig. 5) [81,82].…”

Section: Hindered Aminesmentioning

confidence: 99%

Antioxidants

Kröhnke

Schacker

Zäh

2015

Ullmann's Encyclopedia of Industrial Chemistry

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Transformation of sterically hindered amines (HALS) to nitroxyl radicals: What are the actual stabilizers?

Cited by 8 publications

References 25 publications

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Antibacterial and biocompatible surfaces based on dopamine autooxidized silver nanoparticles

Antioxidants

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