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The dynamics of polymer melts as seen by neutron spin echo spectroscopy
Author(s) -
Ewen Bernd,
Richter Dieter
Publication year - 1995
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19950900110
Subject(s) - reptation , neutron spin echo , polymer , diffusion , intermolecular force , plateau (mathematics) , materials science , neutron , spectroscopy , dynamics (music) , thermodynamics , spin echo , nuclear magnetic resonance , molecule , neutron scattering , chemistry , physics , small angle neutron scattering , nuclear physics , mathematical analysis , mathematics , organic chemistry , quantum mechanics , medicine , radiology , acoustics , magnetic resonance imaging
Using the neutron spin echo spectroscopy, the internal segmental diffusion of chain molecules in polymer melts and concentrated solutions was studied. These investigations show that beyond a characteristic length d t and after a cross over time τ e (d t ) the segmental diffusion of the single chains is strongly impeded and deviates from the Rouse dynamics. d t is polymer specific and depends on the temperature as well as on the polymer concentration. Within the framework of the reptation concept, where d t is identified with the mean distance between intermolecular entanglements or with the tube diameter, the microscopically determined d t ‐values agree quite well with those derived from related macroscopic measurements of the plateau modulus. A similar good agreement is also found with respect to the segmental friction coefficients obtained either from the Rouse regime of the NSE spectra or from Theological data of corresponding short chain systems, where entanglements are not yet effective.