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  • 1
    Electronic Resource
    Electronic Resource
    Quantitative Comparison Between Vacuum-Ultraviolet Irradiation and Remote Hydrogen Plasma Treatment of Hydrocarbon Polymers (1998)
    Springer
    Plasmas and polymers 3 (1998), S. 165-175 
    Details
    ISSN: 1572-8978
    Keywords: Vacuum-ultraviolet ; remote plasma ; polyethylene ; polypropylene ; polystyrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The photon flux of vacuum ultraviolet (VUV) and ultraviolet (UV) radiation of a hydrogen plasma with and without a MgF2window was recorded by fluorescence measurements of sodium salicylate layers. After the compensation of the MgF2absorption by increasing the input power into the plasma source, a comparison between afterglow hydrogen plasma and VUV treatments was made. Polyethylene (PE), polypropylene (PP), and polystyrene (PS) were treated either with VUV radiation or with remote hydrogen plasma and mass loss and CH absorption loss were measured by a quartz crystal microbalance and by infrared reflection absorption spectroscopy, respectively. In the case of PE the effects of both treatments were found to be very similar white for PP slight differences were observed. For the actual set of experimental conditions, the radiation component is largely responsible for the efficiency of the plasma treatment. VUV and remote hydrogen plasma treatments of PS showed only a negligible loss of mass and CH absorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021839228919
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  • 2
    Electronic Resource
    Electronic Resource
    Abfangreaktionen kurzlebiger Radikale, VIII. Über die radikalische Substitution am Stickstoff: Reaktionen von 1-Aryl-triazenen mit Organozinn-hydriden (1972)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 105 (1972), S. 1540-1552 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Short-Life Radicals, VIII. Radical Substitution at the Nitrogen Atom: Reactions of 1-Aryltriazenes with Organotin HydridesStannyl radicals react with 1-aryltriazenes 1-12, attacking N3 and forming stannyl amines. The reaction proceeds by an SH2α mechanism; the arylazo group is displaced (“induced degradation”) and splits off N2. This is the only reaction in cases 1-5. With 6-12, however, an SH2γ displacement predominates. Here, substituents bound to N3 are able to form fairly well stabilized radicals. Stannyl radicals attack N1, displace the substituent from N3 and form trialkylstannyl triazenes 10-12, 15, 20, which are surprisingly stable because of pentacoordination at the tin atom. The free-radical fragments abstract hydrogen from the tin hydride, releasing new stannyl radicals, which propagate the chain reaction. Hydrostannation of the azo group has not been observed. It is shown that stannyl radicals are capable of reversible addition across the azo double bond.
    Notes: Stannylradikale R3Sn⋅ können 1-Aryl-triazene 1-12 and N3 unter Bildung von Stannylaminen angreifen. Dabei wird in einer SH2α-Reaktion die Arylazogruppe verdrängt (“induzierter Zerfall”) und spaltet N2 ab. Dies tritt bei 1-5 ausschließlich ein. Bei 6-12, die an N3 einen als Radikal stabilisierten Substituenten tragen, überwiegt jedoch eine SH2γ-Reaktion. Der Angriff eines Stannylradikals an N1 verdrängt dabei den Substituenten von N3. Es entstehen Trialkylstannyl-triazene 10-12, 15 und 20, durch Pentakoordination am Zinnatom überraschend stabil. H-Abstraktion aus dem Organozinnhydrid stabilisiert die abgespaltenen Molekülfragmente. Die hinterbleibenden Stannylradikale setzen die Reaktionskette fort. Hydrostannierung der Azodoppelbindung wird nicht beobachtet. Es wird gezeigt, daß sich Stannylradikale reversibel an die Azodoppelbindung addieren können.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19721050510
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  • 3
    Electronic Resource
    Electronic Resource
    Abfangreaktionen kurzlebiger Radikale, XI. Über die radikalische Substitution am Stickstoff: Der induzierte Zerfall von 2-Tetrazenen (1973)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 106 (1973), S. 2395-2407 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Short-Life Radicals, XI. Free Radical Substitution at the Nitrogen Atom: The Induced Degradation of 2-TetrazenesThe radical degradation of tetraphenyl-2-tetrazene (1a) and 1,4-dicyclohexyl-1,4-diphenyl-2-tetrazene (1b) is found to be accelerated by trialkyltin hydride. Stannyl radicals attack at N-1 or N-4. In a SH2α reaction, N2, the corresponding stannylamine and a radical ·N(R)R′ are formed. The latter is scavenged by R3SnH giving the amine; or it recombines with a stannyl radical at low hydride concentrations. Dicarbizolyldiazene 1c reacts by the same way, but not so the dipiperidinodiazene (1d). Importance of stabilization of ground and transition states on the spontaneous and the induced degradation are discussed. Values of t1/2, k, ΔH±, and ΔS± are given. Stannyl radicals also accelerate the splitting of tetraphenylhydrazine.
    Notes: Der radikalische Zerfall von Tetraphenyl-2-tetrazen (1a) und 1,4-Dicyclohexyl-1,4-diphenyl-2-tetrazen (1b) wird durch Trialkylzinnhydrid beschleunigt. Beim Angriff von Stannyl-Radikalen an N-1 oder N-4 entstehen in einer SH2α-Reaktion N2, Stannylamin und ein Radikal ·N(R)R′, das durch R3SnH zum Amin abgefangen wird oder mit einem Stannyl-Radikal bei niedriger Hydrid-Konzentration rekombiniert. Auch Dicarbazolyldiazen 1c reagiert analog, nicht jedoch Dipiperidinodiazen (1d). Einflüsse der Stabilisierung von Grund- und Übergangszustand auf den Spontan- wie den induzierten Zerfall werden diskutiert, Werte für t1/2, k, ΔH* und ΔS* angegeben. Auch Tetraphenylhydrazin wird durch Stannyl-Radikale beschleunigt gespalten.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19731060737
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical derivatization as a mean to improve contact angle goniometry of chemically heterogenous surfaces (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 699-709 
    Details
    ISSN: 0887-624X
    Keywords: contact angle goniometry ; chemical derivatization ; plasma treatment ; polyethylene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma-oxidized polyethylene (O-PE) was derivatized with various chemicals and the advancing and receding contact angles with water, formamide, and tricresylphosphate were measured. The contact angles were used to evaluate the surface free energy (SFE) components in terms of the Lifshitz-van der Waals-acid base (LW-AB) model. The derivatization was directed to couple alkyl chains to carbonyl, hydroxyl, and carboxyl groups generated on the surface of O-PE. Carbonyl groups were treated with hydrazine and then reacted with dodecanoyl chloride. Hydroxyl groups were first reacted with reactive dicarboxylic acid dichlorides or cyanuric chloride, respectively, and then with alkylamines because the direct bonding of long-chain alkyl carboxylic acid chlorides proceeds slowly and is, therefore, completed by surface restructuring. Carboxyl groups were chlorinated and in a second step reacted with alkylamines. The bonding of C12-alkyl chains can be sensitively detected by the LW part of the SFE. Concerning the receding contact angles, it is pointed out that the carbonyl groups are present on the surface in a higher concentration than hydroxyl and carboxyl groups. The combination of contact angle goniometry (CAG) and chemical derivatization reactions supplies semiquantitative information about functional groups in the uppermost surface layer. In this way, a major shortcoming of CAG can be overcome. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320408
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  • 5
    Electronic Resource
    Electronic Resource
    Vacuum-ultraviolet induced oxidation of the polymers polyethylene and polypropylene (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2013-2025 
    Details
    ISSN: 0887-624X
    Keywords: vacuum ultraviolet oxidation ; polyethylene ; polypropylene ; plasma-polymer interaction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The emission from low-pressure microwave plasmas in the vacuum-ultraviolet (VUV) region (λ 〈 200 nm) was investigated in order to use these plasmas as light sources for the study of the VUV photochemistry of polyethylene (PE) and polypropylene (PP) as part of the study of plasma-polymer interaction. These polymers, immersed in low-presure oxygen, were exposed to radiation with wavelengths down to 112 nm, the cut off of magnesium fluoride used as a window to separate the polymer specimen from the plasma light source. Total oxygen incorporation in the surface [O], and the formation of hydroxyl, carbonyl, and carboxyl groups were measured using XPS in combination with chemical derivatizations, particularly their dependence upon the radiation spectrum and the oxygen pressure around the sample. In most experiments the surface oxygen concentration [O] attained a constant value that appears to be related to the initial oxidation rate; this suggests a competition between oxygen incorporation and chain scission reactions, followed by the removal of volatile oxidation products. PE is usually oxidized to a higher level than PP, the latter appearing to be more susceptible to reaction with atomic oxygen than PE. A general initiation mechanism for the VUV experiments is proposed that allows us to explain the observed differences in behavior between PE and PP, and the results obtained under different irradiation conditions. The nature of oxidation products is in both cases very similar to what is observed after direct plasma treatment of the polymers. We conclude that short wavelength radiation contributes very appreciably to the observed surface modification effects during plasma treatment of PE and PP. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331208
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