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  • Polymer and Materials Science  (4)
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  • Polymer and Materials Science  (4)
  • Physics  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Preparation, characterization, and porperties of optically active poly(α-methyl-α-ethyl-β-propiolactones) (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 1781-1793 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: S(-) and R(+) enantiomers of α-methyl-α-ethyl-β-propiolactone (MEEPL) were prepared in an eight-step synthesis with respective optical purities of 99 and 97% determined by 1H-NMR (250 MHz) spectroscopy. Polymers (PMEPL) of different enatiomeric compositions were prepared with an anionic-type initiator. Substantial differences in physical properties were observed between the racemic and optically pure polymers; for example, the melting point of the latter is 42°C higher than that of the former. Chiroptical properties of PMEPLs are reported. The 13C-NMR (100.62 MHz) spectra of the polymers indicated that the distribution of configurational units in the macromolecular chain is random.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190717
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Avrami analysis: Three experimental limiting factors (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1655-1657 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.180180715
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Crystallization of poly(α-methyl-α-N-propyl-β-propiolactones) prepared from homogeneous and heterogeneous initiators (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 19 (1981), S. 33-47 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Half-crystallization times t½, enthalpies of fusion ΔH, melting temperatures Tf glass transition temperatures Tg x-ray patterns, and morphologies were obtained for nine samples of poly(α-methyl-α-n-propyl-β-propiolactones) prepared from different homogeneous or heterogeneous initiators. The bulk of the results indicates that all samples can be classified into two categories: Polymers A having t½≏, 100 min, ΔH ≏ 26 J/g, Tf0 ≏ 376 K, Tg ≏ 275 K, and Polymers B having t½ ≏ 10 min, ΔH ≃ 14.5 J/g Tf0 ≏ 425 K and Tg ≏ 271 K. Polymers A were prepared with homogeneous initiators while polymers B were polymerized with heterogeneous intiators. The difference in crystallization behavior between polymers A and polymers B is certainly due to a difference in microstructure, brought about by the initiators, which has been qualitatively observed by NMR.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.180190104
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  • 4
    Electronic Resource
    Electronic Resource
    Complex formation between enantiomeric polyesters (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 22 (1984), S. 577-587 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this study, three different polymers were blended: a racemic PMEPL (PMEPL-RAC) which consists of a random distribution of repeat units of R or S configurations, an isotactic PMEPL made of repeat units of S configuration [PMEPL-S(-)], and a second isotactic PMEPL made of repeat units of R configuration [PMEPL-R(+)]. The acronym PMEPL stands for poly[α-methyl-α-ethyl-βpropiolactone]. The racemic PMEPL is optically inactive but the isotactic PMEPLs are optically active. In the first part of this study, an equimolar mixture of PMEPL-S(-) and PMEPL-R(+) was made. This racemate mixture leads to the formation of stereocomplex between the two polymers which has a melting point roughly 40°C higher than those of the isotactic polymers. The racemate morphology is composed of large spherulites. In the second part of this study, binary blends of PMEPL-S(-) and PMEPL-R(+) were prepared with an excess of one of the isotactic PMEPLs. The stereocomplex is preferentially formed between the isotactic polymers and this complex controls almost entirely the morphology of the sample. The enthalpy of fusion of the stereocomplex in the binary blends can be predicted. however, the excess isotactic polymer is trapped between the lamellae of the spherulites of the stereocomplex and its crystallization is hindered by the high viscosity of the partially crystallized medium. In the third part of this study, ternary blends were prepared. It is shown that PMEPL-RAC does not from a complex with the isotactic polymers. The PMEPL-S(-)/PMEPL-R(+) stereocomplex is again preferentially formed and it controls the morphology of the sample. It decreases the degree of crystallinity of both the excess isotactic polymer and the PMEPL-RAC. This control of the morphology is effective even in samples in which the sterocomplex accounts for only 3% of the total weight of the blend.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.180220404
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    Paper (German National Licenses)
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