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  • 1980-1984  (7)
  • 1950-1954
  • 1981  (7)
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  • 1980-1984  (7)
  • 1950-1954
Year
  • 1
    Electronic Resource
    Electronic Resource
    Micro- and macroconformation of macromolecules (1981)
    Springer
    Polymer bulletin 4 (1981), S. 609-616 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary From the temperature dependence of 13C-NMR chemical shift measurements under fast exchange conditions, using the methyl carbon atom as indicator, it was concluded that for erythrodiisotactic head-to-head tail-to-tail polypropylenes the temperature dependence of the conformers around the methine-methine bond may be analyzed quantitatively. In the present paper the 13C-NMR analysis has been expanded to inverted polypropylenes of arbitrary ditacticity. Methyl, methylene as well as methine resonances have been taken into account for assignements. Conformational influences on the 13C-NMR spectrum are discussed as well as the relevance of low molecular weight models for diads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00256289
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Micro- and macroconformation of macromolecules (1981)
    Springer
    Polymer bulletin 4 (1981), S. 383-390 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A semiempirical modification of FERRY's extension of the ROUSE spectrum in the entanglement region is proposed, with a smooth transition in the relaxation behaviour. Consequently the zero shear viscosity-molecular weight relationship is modelled. With the molecular weight between the entanglements as the only parameter measurements on cis- 1, 4-polybutadiene could be reproduced accurately, comparing favourably with the recent multiparameter theory by SHEN. A simple linear weighting scheme for the average friction coefficient of chemical and configurational copolymers, e. g. cis-trans-polybutadienes, is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254969
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Micro- and macroconformation of macromolecules (1981)
    Springer
    Polymer bulletin 6 (1981), S. 93-100 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The first results are reported about the conformational analysis of an amorphous polymer in the glassy state by means of proton enhanced variable-temperature magic angle spinning 13C NMR experiments. In amorphous threodiisotactic poly(1,2-dimethyltetramethylene) at 220 K different conformational diads could be resolved and assigned. From the spectrum of the glassy polymer the shift increment associated with a conformational change of main chain bonds from anti to gauche is determined. In addition the populations of the conformations of CH-CH bonds and of CH-CH-CH2 bond pairs of poly(1,2-dimethyltetramethylene)s are determined in the glassy state and energy differences between these conformations are estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00256510
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Micro- and macroconformation of macromolecules (1981)
    Springer
    Polymer bulletin 5 (1981), S. 131-135 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Cyclotetracosane exhibits complex phase behaviour in the solid state as well as in the melt as evidenced by complementary methods, DSC, BRILLOUIN scattering, dielectric constant and PE-MAS 13c-NMR. Three solid phases have been verified, one of them — within the range from 299.5 to 312 K — exhibits extremely high molecular mobility. Between the start of melting, 312 K, and the first order transition at ∼ 321 K a mesomorphic type region develops. Two additional transitions have been detected in the melt. That occuring at 361 K (DSC), 356 K (BRILLOUIN data) resembles the Tu as observed in n-alkanes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265156
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Micro- and macroconformation of macromolecules (1981)
    Springer
    Polymer bulletin 5 (1981), S. 125-129 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The proton enhanced magic angle 13C-NMR spectrum of cyclotetracosane exhibits one sharp signal only at room temperature indicating that all carbons within the ring have identical average conformational surrounding at the NMR time scale. A highly mobile pseudorotating phase is concluded. The average ratio of the gauche and of the anti conformers has been calculated from the chemical shift of these cyclotetracosane carbons applying the anti conformer chemical shift of n-alkanes and that of the gauche conformer derived from solution slow exchange spectra of meso 4,5-dimethyloctane. Thus, polyethylene spectra of EARL and VANDERHART could be interpreted in terms of the anti-gauche ratio within the amorphous folds of polyethylene. The conformational balance within the amorphous region of polyethylene is compared with that of erythrodiisotactic poly (1,2-dimethyltetramethylene).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265155
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Micro- and macroconformation of macromolecules (1981)
    Springer
    Polymer bulletin 5 (1981), S. 119-124 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary By applying high resolution solid state 13C-NMR with proton enhancement and with magic angle spinning technique it is demonstrated that the rotational states in semicrystalline polymers may be analyzed for the crystalline as well as for the amorphous phase. In erythrodiisotactic poly (1,2-dimethyltetramethylene) the signals of the chemically different nuclei could be distinguished in the crystalline and in the amorphous regions. The interpretation of the solid state spectrum is consistent with the solution spectrum of the polymer and with that of the analogous low molecular weight compound, meso 4, 5-dimethyloctane, under slow exchange conditions. It is concluded that the crystalline parts of the macromolecular chain exhibit g+aaag−aaag+... conformation (gauches for the CH-CH bond), which is in agreement with the X-ray structure analysis by NATTA et al. Another stable conformation derived from semiempirical atomistic calculations could be excluded for the crystalline phase. An estimation of the conformational balance in the amorphous state has been achieved by comparing the relevant shift data of the solid state erythrodiisotactic poly (1,2-dimethyltetramethylene) with those occuring in the fast exchange spectrum measured in solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265154
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Sol fraction and swelling analysis of cis-1,4-polybutadiene networks produced by high-energy irradiation (1981)
    Springer
    Polymer bulletin 4 (1981), S. 563-568 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Soluble fraction and equilibrium swelling in toluene were investigated on cis-1,4-polybutadiene networks being crosslinked in vacuo by 60Co-irradiation. Analysis of the sol fraction data by means of INOKUTI's equation reveals a drastic increase of the degradation-crosslink ratio for samples unpurified prior to crosslinking. Furthermore, the network crosslinking susceptibility depends on purification, although it is rather temperature insensitive for irradiation above the glass transition temperature of the rubber. The statistics of creation of crosslinks can be examined by suitable modification of INOKUTI's theory. From the present data it may be concluded that chain reaction crosslinking is negligible. The FLORY-REHNER formula for swelling equilibrium fails to reproduce the data at the cross link densities studied, but introducing a free end correction, the formula becomes applicable, with some over-correction. Hence the crosslink susceptibility could be obtained independently if the polymer-solvent heat interaction parameter were known. Additionally, the assumption about the proportionality of the crosslink density with radiation dose has been successfully tested by the swelling experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00284070
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    Paper (German National Licenses)
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