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  • 1
    Electronic Resource
    Electronic Resource
    Spectroscopic measurements on spontaneously polymerizing styrene. Evidence for the formation of two Diels-Alder isomers of different stability (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 939-945 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770331
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  • 2
    Electronic Resource
    Electronic Resource
    Spectroscopic measurements on spontaneously polymerizing styrene, 2.Part 1: cf.1. The estimation of the reactivity of the two Diels-Alder-isomers towards polymer radicals (1977)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 2707-2717 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Spectroscopic measurements at 335 nm on polymerizing styrene have been carried out with spontaneously polymerizing as well as dibenzoyl peroxide (BPO)-initiated bulk systems. The evidence for the formation of two Diels-Alder-intermediates, 1a and 1b, out of which only 1a seems to be capable to produce initiating radicals by reaction with the monomer, can also be derived from the development of the absorption, characteristic for the intermediates, during the BPO-initiated polymerization. From the dependence of the overall rate constants of consumption of 1a, k2,a[M], and 1b, k2,b[M], on the rate of polymerization the reactivity of 1a and 1b towards polymer radicals can be estimated. Whereas 1b, the less reactive intermediate, seems to be mainly consumed by polymer radicals through copolymerization, chain transfer being unimportant, (the rate constant of consumption of 1b by polymer radicals, k3,b, relative to the constant of chain propagation kp ranges from 2,1 at 60°C to 3,2 at 80°C) the corresponding ratio for 1a, k3,a/kp, which goes from 113 at 80°C to 143 at 60°C, is supposed to represent primarily the constant of chain transfer of 1a in styrene polymerization. Under the condition of spontaneous polymerization the reaction with polymer radicals contributes 16% (for 1a) and 5-8,5%, depending on temperature (for 1b), to the overall rate of consumption of the intermediates. The stationary concentration of 1a, the isomer which accordingly is solely responsible for initiation as well as chain transfer in spontaneous styrene polymerization, is calculated to range from 5,2·10-6 mol l-1 at 60°C to 8,5·10-6 mol l-1 at 80°C.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1977.021780920
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  • 3
    Electronic Resource
    Electronic Resource
    Untersuchungen zur Thermolyse und zur Sauerstoff-Stabilität der 4π + 2π-Diels-Alder Addukte des Styrols (1977)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 3007-3016 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 4π + 2π-Diels-Alder cycloadduct 1 involved in the spontaneous polymerization of styrene was investigated under conditions, where bimolecular reactions with styrene leading to a consumption of 1 can be neglected. For this reason 1 was (a) submitted to thermolysis in an inert solvent (toluene) at different temperatures (90, 100 and 110°C) and (b) oxidized with an excess of oxygen in styrene at room temperature. The reactions were followed spectrometrically at the wavelength λ = 325 nm and analyzed in terms of a first order reaction. The results show strong evidence for the involvement of two diastereomers (1a and 1b) of different reactivity. This is in qualitative and quantitative agreement with the two isomers' concept, which had been deduced previously from kinetic analysis of the formation of 1 during the thermal polymerization of styrene. Rate constants and activation energies as well as possible reaction pathways are given.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1977.021781105
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  • 4
    Electronic Resource
    Electronic Resource
    Acrylsäure-popcornpolymere, 2Teil 1: cf.1.. Oberflächenstruktur der glasigen und der popcorn-polymeren (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 2787-2792 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: By scanning electron microscopy characteristical differences are shown in the surface structure of three types of polymers - opaque, glassy, popcorn - obtained by polymerization of acrylic acid in bulk and in mixtures with water. These differences are related to the mechanism of formation of the polymers.
    Notes: Durch Rasterelektronenmikroskopie werden die charakteristischen Unterschiede der Oberflächenstruktur der durch Polymerisation von Acrylsäure in Substanz und in Mischung mit Wasser erhaltenen Polymertypen - opak, glasig, Popcorn - gezeigt. Diese Unterschiede stehen in Beziehung zum Bildungsmechanismus der Polymeren.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770920
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  • 5
    Electronic Resource
    Electronic Resource
    The Diels-Alder intermediate as a chain transfer agent in spontaneous styrene polymerization 1. New evidence from the kinetic analysis of photoinitiated polymerization (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 3065-3071 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021771021
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanismus der photopolymerisation des styrols, 4Teil 3: cf.3.. Zur rolle der photo-(4π + 2π)-addukte als kettenüberträger und zur kinetik der photopolymerisation in gegenwart überlagerter, thermischer prozesseHerrn Prof. Dr. J. W. Breitenbach, meinem verstorbenen Lehrer, in Dankbarkeit und tiefer Wertschätzung gewidmet. (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2695-2705 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photopolymerization of styrene was investigated at 25°C, by following the variations in the rate of polymerization and the degree of polymerization with the light intensity, JM, at different wavelengths of the exciting light (λe = 313 nm, λe = 335 nm). The corresponding data were analyzed in terms of the formalism between the rate RP and the viscosity average degree of polymerization Pη. The kinetic evaluation shows that at least at small fractions of the absorbed light and at short duration of the irradiation the stabilization of the growing chain radicals will occur predominantly by bimolecular termination processes and not by chain transfer. This must be attributed to the fact that among the four theoretically possible isomeric photo-(4π + 2π)-intermediates (I) 1-phenyl-1,2,3,8a-tetrahydronaphthalene (diastereomers 1a and 1b) and 2-phenyl-1,2,3,8a-tetrahydronaphthalene (diastereomers 1′a and 1′b) the photostationary concentration [1a]∞ of the most reactive chain transfer agent 1a is - as a result of its very small quantum yield of formation (ϕ1a ≪ ϕ1b + ϕ1′a + ϕ1′b) - extremely low and contributes only a few percent to the total photo-steady-state concentration of I. At higher temperatures (T 〉 25°C) and at small fractions of the absorbed light JM/Jo (λe = 335 nm), the rate of photopolymerization RP is controlled by the contributions of two independent routes of initiation: (1) the rate RSI, which accounts for the photo-free radical formation of the photo-intermediates I, and 2 the rate RS1, which is derived from the photoinduced free radical generation of the thermally produced Diels-Alder adducts 1a and 1b. As a further aspect of this analysis the results give strong evidence that the endo adduct 1a, when electronically excited, enters into a very efficient radical forming process, contrary to the other isomers 1b, 1′b, and 1′a, which seem to be mainly deactivated by their individual retro-Diels-Alder decompositions and will not enter into free radical formation to any noticeable extent: ϕS1a ≫ (ϕS1b + ϕS1′b + ϕS1′a) An explanation of the very different stereodynamic behaviour is given.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021801111
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  • 7
    Electronic Resource
    Electronic Resource
    Mechanismus der photopolymerisation des styrols, 1. Zur desaktivierung elektronisch angeregten styrols durch chemische konzentrations-löschprozesse: Photooligomere und photopolymereHerrn Prof. Dr. O. E. Polansky mit den besten Wünschen zum 60. Geburtstag gewidmet. (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2649-2663 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electronically excited styrene - in bulk or in concentrated solution - via intermolecular fluorescence self quenching processes undergoes a series of parallel and consecutive chemical reactions, leading to photooligomers and photopolymers. The oligomeric photoproducts, as shown by gas chromatography analysis, consist of dimers (M2) and trimers (M3) of styrene, whereby the quantity of M2 exceeds M3 by a factor of 20. The dimer fraction is built up of (a) 4 non olefinic cyclic C16-hydrocarbons: cis-1,2-diphenylcyclobutane (c-CB, 45-50 wt.-%), trans-1,2-diphenylcyclobutane (tr-CB, 8-10 wt.-%), 1-phenyl-1,2,3,4-tetrahydronaphthalene (1-PhT, 7-9 wt.-%), and 2-phenyl-1,2,3,4-tetrahydronaphthalene (2-PhT, 3-5 wt.-%), (b) an open chain unsaturated compound-1-vinyl-2-(2-phenylethyl)benzene (VPEB, 5-7 wt.-%), and (c) 5 highly unsaturated mono-, bi-, and/or tricyclic C16-valence isomers (19-32 wt.-%) which are considered to be the result of the participation of the aromatic benzene system in 1,2-, 1,3- or 1,4-photocycloaddition reactions, respectively. Among the numerous phototrimers, two saturated C24-hydrocarbons were identified: 1-phenyl-4-(1-phenylethyl)-1,2,3,4-tetrahydronaphthalene (T1) and 2-phenyl-4-(1-phenylethyl)-1,2,3,4-tetrahydronaphthalene (T2). Under conditions where simultaneous thermal processes could be excluded (-20≤T/°C≤25), the presence of 1-PhT, 2-PhT, T1 and T2 gives strong evidence for the involvement of two 4π + 2π-photointermediates, viz. 1-phenyl-1,2,3,8a-tetrahydronaphthalene (1) and 2-phenyl-1,2,3,8a-tetrahydronaphthalene (1′), which undergo two consecutive reactions: (a) a unimolecular, photo-induced 1,3-sigmatropic rearrangement (1-PhT, 2-PhT) and (b) a bimolecular, photo-induced ene-reaction with styrene as enophilic component (T1, T2). Because of the non-concerted, stepwise nature of this photo-ene-process, the trimers have to be interpreted as the products of a cage reaction between two radical pairs |R1…R2| and |R1…R2′|. Their presence therefore gives strong evidence that the non-concerted ene-reaction is the most probable pathway for the production of the free radicals, which are responsible for the initiation of photopolymerization.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021801108
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  • 8
    Electronic Resource
    Electronic Resource
    Acrylic acid popcorn polymers (1974)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 2597-2604 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polyacrylsäure ist in seinem reinen Monomeren nicht löslich. Bei der Polymerisation von Acrylsäure in Substanz entstehen nebeneinander transparentes glasiges und opakes Polymers, aber kein Popcornpolymeres. Durch Zusatz von Wasser zum Monomeren wird die Bildung und Proliferation von Popcornpolymeren während der Polymerisation bewirkt. Die Entstehung von Popcornpolymeren wird auf das bessere Lösungsvermögen des Monomer/Wasser-Gemisches für die Polyacrylsäure im Vergleich zur Lösungsmittelqualität des reinen Monomeren zurückgeführt.
    Notes: Poly(acrylic acid) is not soluble in the pure monomer. In the polymerization of acrylic acid in bulk, both glassy and opaque polymer is obtained but no popcorn polymer. Formation and proliferation of popcron polymer takes place during polymerization by adding water to the monomer. The better solvent quality of the monomer/water mixture for poly(acrylic acid) compared to the solvent quality of pure monomer is considered to be the cause for popcorn polymer formation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1974.021750907
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  • 9
    Electronic Resource
    Electronic Resource
    Mechanismus der photopolymerisation des styrols, 2Teil 1: cf.1. Zur photochemie und photokinetik der intermediären photo-(4π + 2π)-addukte des styrolsHerrn Prof. Dr. J. W. Breitenbach, meinem verstorbenen Lehrer, in Dankbarkeit und tiefer Wertschätzung gewidmet. (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2665-2680 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The unsensitized photoinitiation of styrene polymerization is accompanied by the formation of some typical oligomeric key substances, which are indicative of two 4π + 2π-photo-intermediates (I), viz. 1-phenyl-1,2,3,8a-tetrahydronaphthalene (1) and 2-phenyl-1,2,3,8a-tetrahydronaphthalene (1′). Owing to the very different absorption coefficients of monomer and I, formation and consumption and, therefore, the photo stationary concentration of I exhibits a pronounced dependence on the wavelength λe of the light used for irradiation. Under conditions, where the exciting light is not homogeneously but totally absorbed in the system (λe = 291 nm, corresponding to the 0-0 band of the lowest 1Lb←1A transition in styrene), the intermediates I can be enriched to such an extent, that they are detectable not only by UV-absorption (310≤/nmλ/nm ≤ 360) but also - with the aid of a special high vacuum technique - by 1H NMR spectroscopy, which gives unambiguous proof for the molecular structure suggested for I. Moreover, the photochemistry, the photokinetics and the photophysical behaviour of I were investigated in detail. In the absence of any fluorescence (ϕFI 〈 10-4) of the intermediate the overall quantum yield for consumption was found to be ϕ-1 = 1. It is shown, that the photo-retro-Diels-Alder process is the dominating reaction (ϕ2M = 0,94) and the 1,3-H-sigmatropic rearrangement does not contribute more than ϕPhT≤0,06. Together with the mean natural molar absorption coefficients ϕI = 18400 dm3·mol-1·cm-1 for λ = 313 nm and ϕI = 7300 dm3·mol-1·cm-1 for λ = 335 nm the photostationary concentration [I]∞ is calculated to range from [I]∞ = 8,7.10-6 mol. dm-3 at λe = 313 nm to [I]∞ = 1,2.10-6 mol.dm-3 at λe = 335 nm, which proved to be independent of the intensity of the incident light J0.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021801109
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  • 10
    Electronic Resource
    Electronic Resource
    Mechanismus der photopolymerisation des styrols, 3Teil 2: cf.8.. Zur kinetik der photo-elementarprozesseHerrn Prof. Dr. J. W. Breitenbach, meinem verstorbenen Lehrer, in Dankbarkeit und tiefer Wertschätzung gewidmet. (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2681-2693 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photoinduced free radical bulk polymerization of styrene (M) - in the absence of any sensitizer or free radical initiator - was investigated at different intensities, Ja, and at different wavelengths, λe, of the exciting light (λe = 313 nm, 335 nm; 25°C). The polymer conversion was followed dilatometrically in optical cells and the photo-oligomers which are built up simultaneously in the polymerizing system  - cis-1,2-diphenylcyclobutane (c-CB), trans-1,2-diphenylcyclobutane (tr-CB), 1-phenyl-1,2,3,4-tetrahydronaphthalene (1-PhT), 2-phenyl-1,2,3,4-tetrahydronaphthalene (2-PhT), 1-phenyl-4-(1-phenylethyl)-1,2,3,4-tetrahydronaphthalene (T1) and 2-phenyl-4-(1-phenylethyl)-1,2,3,4-tetrahydronaphthalene (T2), - were quantitatively analyzed by GLC. The quantum yields were found to be ϕc-CB = 0,10, ϕtr-CB = 0,02, Φ1-PhT = 0,0084, Φ2-PhT = 3,7.10-3, ΦT = 5,0.10-4, respectively, and from the experimentally observed dependence of the rate of polymerization, VP, on the square root of the light intensity, Ja, the apparent quantum yield of the formation of radicals can be calculated to be ΦS = 5,6.10-4. On the basis on the proposed structure of the photointermediates, I, which had been previously confirmed by 1H NMR spectroscopy in enriched systems, the kinetic treatment of the photostationary state gives a complete data set of mean values of partial quantum yields, ϕ, concerning all the photo-elementary processes of I under polymerizing conditions: ϕS = 2,56.10-3, ϕT = 2,3.10-3, ϕPhT = 5,5.10-2 and ϕ2M = 0,94 (retro-Diels-Alder decomposition).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021801110
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