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  • Articles  (660)
  • Physics  (660)
  • ASTRONOMY
  • 1985-1989  (58)
  • 1980-1984  (339)
  • 1970-1974  (263)
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  • 11
    Electronic Resource
    Electronic Resource
    Lyotropic mesomorphic formation of cellulose in trifluoroacetic acid-chlorinated-alkane solvent mixtures at room temperature (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 19 (1981), S. 1231-1236 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mixtures of trifluoroacetic acid (TFA)-1,2-dichloroethane (1,2-DCE); TFA-dichloromethane (CH2Cl2); and TFA-trichloromethane (CHCl3) are excellent cellulose solvents at room temperature. TFA-1,2-DCE and TFA-CH2Cl2 are superior to pure TFA. Lyotropic cellulose mesophases were obtained in (20% w/v) solutions of cellulose in these solvent mixtures. The optical and optical rotatory powers of the solutions suggest that the lyotropic mesophase of cellulose is cholesteric. This implies that cellulose molecules are arranged in helical form in these solvent systems.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.180190806
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  • 12
    Electronic Resource
    Electronic Resource
    Microphase separation in sulfonated polystyrene ionomers (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 1503-1509 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.180200815
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  • 13
    Electronic Resource
    Electronic Resource
    Structure and morphology of heavily deformed single crystals of a polydiacetylene. I. Electron microscopy and x-ray diffraction (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 19 (1981), S. 293-305 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structure and morphology of heavily deformed single crystals of a diacetylene polymer have been studied using a combination of x-ray diffraction and electron microscopy. Crystals have been deformed by both rolling and hammering. The crystals remain intact during deformation and can be reduced in thickness by a factor of over 5 in directions perpendicular to their chain axes. It is found that the chain orientation is maintained during both hammering and rolling. A greenish-colored surface skin develops during both types of deformation but the structure of the interior of the crystals depends upon the type of deformation employed. The interior of the hammered crystals consists of crystal blocks ca. 50 μm thick formed by cleavage perpendicular to the chain direction whereas the rolled crystals tend to be fibrous with no evidence of molecular fracture. The possible deformation mechanisms which have given rise to the different structures have been discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.180190210
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  • 14
    Electronic Resource
    Electronic Resource
    Mesomorphic solutions of cellulose triacetate in halogenated organic acids and mixtures of trifluoroacetic acid and dichloromethane (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 19 (1981), S. 1449-1460 
    Details
    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 liquid-crystalline solutions in trifluoroacetic acid, dichloroacetic acid, and mixtures of trifluoroacetic acid and dichloromethane. Brilliant iridescent coloration, high optical rotations, and birefringent regions with swirl-like fingerprint patterns suggested the formation of cholesteric liquid crystals. Trifluoroacetic acid-dichloromethane is a particularly excellent solvent mixture to form liquid-crystal solutions of cellulose acetate. Crude bulk viscosity measurements confirm the formation of an anisotropic phase, and the temperature dependence of the critical concentration for formation of the anisotropic phase, obtained by bulk viscosity measurements at various temperatures, provides confirming evidence. Viscosity decreases with aging, suggesting that CTA is slowly degraded in the solvents studied. This is also confirmed by optical rotatory measurements and by polarizing microscope observations. The miscibility gap is observed as a function of molecular weight, and the differences between the experimental data and Flory's prediction are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.180190916
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  • 15
    Electronic Resource
    Electronic Resource
    Spectroscopic study of rigid-rod polymers. II. Protonation effect (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 509-521 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.180200312
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  • 16
    Electronic Resource
    Electronic Resource
    Investigation of molecular order in liquid-crystalline solutions of cellulose triacetate using PMR spectroscopy (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 1019-1028 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.180200610
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  • 17
    Electronic Resource
    Electronic Resource
    Conformation of polystyrene with special emphasis to the near all-trans extended-chain model relevant in polystyrene gels (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 71-82 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In light of novel and problematic diffraction patterns arising through the thermoreversible gelation of isotactic polystyrene, the conformational possibilities were examined with particular reference to other conformational works published recently on this polymer. The specific objective was to ascertain whether highly extended, helical backbone geometries such as are required by the new x-ray patterns are possible or not with a purely isotactic arrangement of side groups. The first realization was that the recently announced low-energy, near-trans conformations are not relevant to the present issue as they do not provide the required extended geometry. Further, specific sampling of the conformational energy map revealed that the required high chain extension may be energetically feasible, contrary to traditional conceptions and to recent conformational calculations elsewhere. The divergences as regards the latter were traced to the specific choice of nonbonded atomic radii - all within generally accepted limits - which accordingly has a crucial effect even to the extent whether specific conformation types are forbidden or energetically stable. The implications this has for conformational analysis in general are being pointed out. While the novel crystal structure has not been solved, the present study at least eliminates the previously believed categoric objections to it being associated with isotactic chains and, beyond this, opens up new perspectives as regards conformational possibilities in polyolefins. The more general problems concerning the nature and origin of the gelation phenomenon nevertheless remain.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.180180106
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  • 18
    Electronic Resource
    Electronic Resource
    Far-infrared studies of microphase separation in sulfonated ionomers (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 1869-1881 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Far-infrared spectra of a series of un-neutralized and neutralized lightly sulfonated polystyrenes with varying sulfonation levels have been investigated to seek spectroscopic evidence for microphase separation known to control the physical properties of these polymers. Broad, strong absorbance bands, not found in the spectrum of unmodified polystyrene, are observed in the spectra of the sulfonated analogs. The effects on the far-infrared spectra both of sulfonation level and of the mass and charge of the neutralizing cation are discussed in terms of cation motion and the formation of ion-rich domains.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.180230911
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  • 19
    Electronic Resource
    Electronic Resource
    Electrical properties of ion-implanted poly(p-phenylene sulfide) (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 537-551 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.180210405
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  • 20
    Electronic Resource
    Electronic Resource
    The dependence of dielectric response of an elastomer on hydrostatic pressure (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 1195-1203 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.180210718
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