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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 895-899 
    ISSN: 1573-4846
    Keywords: luminescence ; pyranine ; sol-gel ; hybrid coatings ; emission anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The sensitivity of the pyranine fluorescence to protonation/deprotonation is used to follow modifications in cured sol-gel thin films. The acid concentration in the sol-gel solution is varied for TEOS-based coatings and a series of organically modified silanes Si(OR)3R′ are added to the TEOS solution. The concentration of the organically modified silane is varied as well as the chain length of the alkylgroup (R′). The stationary fluorescence measurements show that the equilibrium between the protonated and the deprotonated form of pyranine changes depending on the type of silica matrix. The deprotonated form is dominant in the cured SiO2 films and the protonation/deprotonation ratio of pyranine is constant for the different acid concentrations used. The protonated form becomes dominant as the concentration of Si(OR)3R′ is increased and as the alkyl chain length (R′) of the organically modified silanes is augmented. Emission anisotropy measurements of pyranine in the same coatings show that the rotational freedom of the molecule changes due to modifications in the cages for the TEOS-based coatings. These modifications are produced by the acid concentration used to prepare the coatings. An increase in the rotational freedom of pyranine is observed in the TEOS-Si(OR)3R′ systems.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 3 (1979), S. 85-106 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Different modes of interaction between the realm of photochemistry and photophysics and the domain of polymer chemistry are discussed. A distinction between photoinitiation and photopolymerization is drawn on the basis of the role of the excited state either in the chain starting or chain-growing process. Attention is drawn to specific properties or problems in the photochemistry and photophysics of macromolecules. The influence of neighbouring groups, high local concentrations etc. are discussed in relation to polymer transformation and excimer formation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 13 (1985), S. ix 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dipeptides of the aromatic fluorescent amino acid, pyrenylalanine, are studied using both stationary and transient fluorescence techniques. Since the conformational transitions of the peptide chain are slow compared to the decay of the pyrene excited state, both ground state conformations, adopted by the peptide, i.e., C5 and C7, can be monitored separately. Kinetic models are proposed to describe the molecular dynamics of the peptide chain as probed by the intramolecular excimer formation between both pyrene chromophores. These kinetic schemes explain the influence of solvent, chain chirality, main chain-side chain interactions, and nature of the protecting groups on the emission spectrum and the fluorescence decay profile of these model peptides. These schemes also provide a tool to calculate rate constants of conformational transitions and excimer formation. By comparing the kinetic and thermodynamic parameters of the various compounds, the influence of a structural modification on the molecular dynamics of the peptide chain is determined.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 13 (1975), S. 215-225 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the photoreduction of benzophenone and the reductive photopolymerization of diaryl ketones are closely interrelated. The photoreductive polyrecombination presents the characteristics of a polycondensation, namely, an increase in molecular weight with reaction time. In the absence of side reactions, benzophenone and diketone Ia show identical behavior toward hydrogen abstraction, as is reflected in the di-bis rate constants of hydrogen abstraction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 13 (1975), S. 227-252 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The irradiation of nonconjugated bichromophoric systems, diaryl ketones, with ultraviolet light in the presence of hydrogen donors, such as isopropanol or bisbenzhydrol, yields high polymers. Two series of arylketones were investigated, namely bisbenzophenones and bisketotriazoles. The cage reaction, which arises from the cross combination between the acetone ketyl and bisbenzophenone ketyl radicals, was estimated to be very small but may constitute a chain termination reaction in the photopolymerization in isopropanol. The photopolymerization of bisdiketone-dihydrol systems was found to yield polymers with much higher molecular weights than those obtained from the photopolymerization of bisdiketone-isopropanol systems. The photolysis of some binary mixtures of aromatic diketones in the presence of isopropanol yielded statistical copolypinacols. In some favorable cases, the NMR spectrum of the copolymer obtained showed three distinct linkages and from the infrared spectrum intensities the copolymers composition and the number average length of the sequences may be determined.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 6 (1968), S. 547-550 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 9 (1971), S. 777-780 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 10 (1972), S. 669-673 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 13 (1975), S. 201-213 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-state photoreactivity of a series of maleimides and bismaleimides is studied Various crystalline maleimides are found to dimerize on irradiation by ultraviolet light Based on this discovery, the photopolymerizability of the related bismaleimides in the crystalline state is examined. As a result it is found that some N,N,-alkylenebismaleimides polymerize into highly crystalline polymers. The polymers do not melt below their decomposition temperature (〉300°C) and are practically insoluble in all solvents. The obtained irradiation products are different from the reaction products of the solution-phase photochemistry. Closely related bismaleimides, such as members of a homologous series, show substantial differences in their solid-state photochemical behavior; on excitation they either lead to polymers or are not reactive. This indicates that the solid-state photoreactivity of maleimides and bismaleimides is controlled by the geometry of their crystal structure.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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