Kinetics of reversible surface crystallization and melting in poly(ethylene oxide): Effect of crystal thickness observed in the dynamic heat capacity |
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Authors: | T Albrecht S Armbruster S Keller G Strobl |
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Institution: | Fakult?t für Physik, Albert-Ludwigs-Universit?t, 79104 Freiburg, Germany, DE
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Abstract: | Poly(ethylene oxide) (PEO) in the semi-crystalline state shows a reversible surface crystallization and melting; a temperature
decrease leads to a certain crystal thickening, a temperature increase reversely to an expansion of the amorphous intercrystallite
layers. Dynamic calorimetry provides a means to investigate the kinetics of the process. The structural rearrangement in the
region of the crystalline-amorphous interface can only be accomplished if the chains can slide through the crystallites. One
therefore expects the associated time to change with the crystallite thickness. Variations of the crystal thickness of PEO
can be achieved by choosing different crystallization temperatures. We studied the effect of the crystal thickness employing
temperature-modulated differential scanning calorimetry and heat wave spectroscopy, and by carrying out small-angle X-ray
scattering experiments for the structural characterization. The effect of the crystal thickness is clearly observed. Results
indicate that the sliding diffusion through the crystallites takes place by helical jumps of whole stems. Data yield the activation
energy per unit length of the stems.
Received 20 April 2001 and Received in final form 13 August 2001 |
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Keywords: | PACS 61 41 +e Polymers elastomers and plastics |
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