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  • Physics  (148)
  • 1980-1984  (148)
  • 1950-1954
  • 1930-1934
  • 1983  (79)
  • 1982  (69)
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 3033-3033 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 575-582 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hindered amine-induced decomposition of polypropylene hydroperoxide was studied in the solid state and in the presence of a liquid solvent and the polymer was compared with model hydroperoxides. The high reactivity of the macrohydroperoxides appears to be related to the adjacent, hydrogen-bonded hydroperoxide groups that occur in the polymer. The hindered amines are converted to nitroxides in the reaction via hydroxylamine intermediates. Amine-induced decomposition of polypropylene hydroperoxide is faster in the absence of a liquid solvent for the amine than in the presence of the solvent, probably because of the strong amine-hydroperoxide association that occurs in the solid state. The decomposition process in the solid state is sufficiently rapid for the reaction to contribute to the effectiveness of hindered amines in the light stabilization of polymers.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 509-521 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The protonation of a heterocyclic rigid-rod polymer poly(p-phenylene benzbisthiazole) and its model compound has been studied by UV-visible and Raman spectroscopy. Because of the two nitrogens on the heterocyclic ring, spectroscopic features of unprotonated, half-protonated, and fully protonated structures have been identified. For the fully protonated molecule, there is also an increase in conjugation between the phenyl ring and the heterocyclic ring.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 1079-1090 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Cellulose triacetate (CTA) forms cholesteric mesophases in trifluoroacetic acetic acid (TFA) and mixtures of TFA and CH2Cl2, 1,2-dichloroethane (1,2-DCE), and CHCl3. Cholesteric pitches and solution flow times indicate that the order of solvent powers is TFA-CH2Cl2 〉 TFA-1,2-DCE 〉 TFA 〉 TFA-CHCl3, which is the order of decreasing acidity of the solvent systems. With TFA-CH2Cl2 as solvent, the one-fourth power of the pitch varies inversely with the CTA concentration, and increases linearly with temperature. The pitch increases exponentially with time and increases faster the more acidic the solvent. In a magnetic field a cholesteric to nematic transition occurs. A minimum in solution viscosity occurs at 34% w/v of CH2Cl2 for solutions in TFA-CH2Cl2. The miscibility gap as a function of molecular weight depends on the solvent composition and is smaller the higher the acidity of the solvent. Agreement between the experimentally observed A and B points and the theoretical points is better for the Khokhlov and Semenov theory for semiflexible chains than for the original Flory theory or the Flory-Ronca modification.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 1019-1028 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Liquid-crystalline solutions of cellulose triacetate (CTA) in trifluoroacetic acid (TFA)-CH2Cl2, TFA-1.2-dichloroethane (1,2-DCE) solvent mixtures were examined by means of PMR spectroscopy. CTA forms both cholesteric and nematic phases in these solvents depending on the CTA concentration. In cholesteric solutions the CH2Cl2 signal is initially a singlet and then splits into a doublet. The time dependence of the splitting and the effect of CTA concentration are reported. The results suggest that the cholesteric phase slowly changes into a nematic phase in the magnetic field. The splitting of the CH2Cl2 proton signal into a doublet and the 1,2-DCE signal into a quartet are due to direct magnetic dipole-dipole interactions. Rotation of the sample in the magnetic field results in the disappearance of the doublet or quartet and suggests that the solvent molecules are originally oriented in the direction of the magnetic field. In the biphasic region, immediate splitting of the CH2Cl2 proton signal suggests that the anisotropic phase is nematic.
    Additional Material: 8 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 537-551 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ion implantation of impurities into thin films of poly(p-phenylene sulfide) (PPS) is found to increase the conductivity of the material by up to 12 orders of magnitude. The increase is stable under exposure to ambient conditions, in contrast to the instability of the conductivity increases in PPS produced by chemical doping with AsF5. PPS films 0.1-0.2 μm thick are spin cast from solution onto interdigitated electrodes patterned on an oxidized silicon substrate. The room-temperature interelectrode resistance is measured as a function of implantation fluence. An estimate of film conductivity is obtained from this resistance with a simple model for the electrode and film geometry. A first experiment yielded similar conductivity increases for implantation of either arsenic or krypton. At a fluence of 1 × 1016cm-;2, which corresponds to an average impurity concentration of 2.5 × 1021cm-3, the conductivity reaches an apparently saturated value of 1.5 × 10-5 (Ω cm)-1. Infrared spectra of the films before and after implantation suggest that crosslinking may be present in the implanted films, and Auger studies show stoichiometric changes throughout the implanted layer. These results suggest that the observed conductivity changes are the result of molecular rearrangements produced by the implantation rather than the result of specific chemical doping. Specific chemical doping may, however, explain the results of a second experiment in which implantation of bromine resulted in substantially larger conductivities found to increase at an approximate linear rate from a value of 1.0 × 10-4 (Ω cm)-1 at a fluence of 1 × 1016 cm-2 to a value of 4.0 × 10-4 (Ω cm)-1 at a fluence of 3.16 × 1016 cm-2.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 1195-1203 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dielectric methods have been employed to study the high-pressure behavior of a polyurethane elastomer (Solithane 113) in the vicinity of its α transition. The α-loss peak is shifted to higher temperatures and broadened somewhat with the application of hydrostatic pressure up to 6.4 kbars. The slope of Tα vs. P, or dTα/dP, obtained at low frequencies was found to be equal to dTg/dP obtained by a volumetric method. Moreover, it attained a nonzero limiting value at high pressures for each frequency tested (3 - 30,000 Hz) and the limiting value itself increased with increasing frequency from 10.5°C/kbar at 3 Hz to 18°C/kbar at 30,000 Hz. The activation enthalpy ΔH* was found to be nearly constant over the pressure range tested, but the activation volume ΔV* decreased with increasing pressure. The relation dTα/dP = T (ΔV*/ΔH*) was shown to hold for the elastomer.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 1503-1509 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small- and wide-angle x-ray scattering results for a series of un-neutralized and neutralized sulfonated polystyrenes are presented for the range of sulfonation from 0 to 7.26 mol %. From the small-angle scattering it is shown that above the 3 mol % level for both the zinc and sodium salts, a Bragg spacing (37 Å) and diameter (6.9-8.4 Å) of the scattering unit can be calculated. When the concentration of salt is increased, there is no appreciable change in the latter two measurements. The wide-angle data indicate that the cations do not influence to any large extent the basic intramolecular and intermolecular structure of polystyrene. All the data are consistent with the onset of clustering above a critical ion concentration.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 2607-2607 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    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 20 (1982), S. 939-950 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The grafting of styrene and acrylamide, from both their binary and unitary systems, on cellulose acetate film was studied by means of the cobalt-60 postirradiation grafting technique. The extent of grafting was found to be dependent on preirradiation dose, reaction time, and temperature, and the optimum conditions were evaluated. The effect of solvents, e.g., water, methanol, ethanol, isopropanol, and t-butanol were studied. The composition of the binary mixture as well as the nature of the alcohol used as the solvent were found to have a strong influence in modifying the course of grafting. Each component of the binary monomer mixture was found to sensitize the grafting of the other, when the former is present in relatively large concentration. The observed results are discussed in detail in terms of relative molecular reactivity and reactivity ratios.
    Additional Material: 10 Ill.
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