Abstract
The dependence of the molecular motion of polyurethane on the length of methylene chain in the monomer unit and on the molecular weight has been studied by the broad line nuclear magnetic resonance, NMR, dynamic loss modulus, E″, wide angle X-ray scattering, and the density.The second moment, ‹ΔH2›, at the rigid state increases with an increasing number of methylene groups.The degree of narrowing of ‹ΔH2› for the secondary dispersion increases with increasing numbers of methylene groups. This agrees with the theoretical prediction based on the local mode motion of the main chain. The force constant of the local mode motion of the polymethylene chain thus estimated is 3.0×1013 erg. The dispersion of the dynamic loss modulus at about −135°C corresponds to the above secondary dispersion of ‹ΔH2›.The primary dispersion temperature decreases with decreasing molecular weight.
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Nagura, M., Wada, E. Molecular Motion in Amorphous Polyurethane. Polym J 4, 115–119 (1973). https://doi.org/10.1295/polymj.4.115
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DOI: https://doi.org/10.1295/polymj.4.115
