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  • 1
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electron spin resonance (ESR) observations of the solid-state thermal polymerization of bis(p-toluene sulphonate) of 2,4-hexadiyne-1, 6-diol at 60°C, 70°C, and 80°C are reported. The weak paramagnetism observed in polycrystalline samples is interpreted in terms of departures of the polymer chain from an equilibrium conformation. Decomposition occurs at 70°C and 80°C during the final phase of polymerization producing additional paramagnetic centers. Lineshape parameters measured during polymerization show changes which we attribute to changes in the delocalization and mobility of the paramagnetic center. We conclude that the nature of paramagnetism in crystalline conjugated diacetylene polymers is a chain defect property characteristic of interband electronic states close to the valence band.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solid-state thermal polymerization of 2,4-hexadiyne-1, 6-diol has been studied by a variety of methods. Pure monomer heated under vacuum or in an inert gas atmosphere is found to polymerize readily, unlike material heated in air. X-ray diffraction reveals that samples anneal during polymerization. Initially, a long chain polymer is formed, but above 20% conversion a less perfect product is obtained. Measurements suggest a complex molecular rearrangement during the nonideal phase of polymerization. Possible models for this process are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The existence of local order in two epoxy resins of the diglycidyl ether of bisphenol-A (DGEBA) type has been investigated using Rayleigh scattering and Brillouin spectroscopy. The resins differ in their molecular weight distributions and their relative concentrations of epoxide and hydroxyl groups. The complementary use of both techniques in elucidating the thermal behavior of local order is illustrated, and the use of the latter technique to study thermal acoustic phonons and hypersonic relaxation is discussed. Both techniques independently show that molecular aggregates exist in each resin system. The scattering-envelope dissymmetry shows that the resin with the high epoxide/hydroxyl group ratio contains aggregates up to 20 nm in size, and the low-ratio resin exhibits sizes up to 70 nm. These aggregates are thermally unstable in the temperature range studied (293-443 K). Dissolution in chloroform shows that these aggregates are reduced in size and that further structural changes occur which are dependent on solvent concentration. Aggregate volume fractions were determined for a range of aggregate size. Brillouin spectroscopy indicated that both resins exhibit hypersonic relaxation in the temperature range studied. The complex longitudinal moduli of the resins were superimposable under a WLF temperature transformation comparable to the difference in their static glass transition temperatures. Molecular aggregate size, number, and stability are related to the epoxide/hydroxyl ratio of the resins and the degree of intermolecular hydrogen bonding.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal degradation of the monomer and polymer of bis(p-toluenesulfonate) of 2,4-hexadiyne-1,6-diol has been investigated. Decomposition during the latter stages of solid-state thermal polymerization at 80°C and of 100% polymer at 112°C was observed by mass spectrometry and the decomposition fragments identified. Mechanisms for this low-temperature degradation are suggested. Pyrolysis of the monomer and polymer between 400 and 1000°C was studied by gas chromatography and mass spectrometry. The principal pyrolysis products are triacetylene and p-toluenesulfonic acid. The fragmentation routes leading to and derived from these products are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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