Eur. Phys. J. E 6, 237-243 (2001)
Kinetics of reversible surface crystallization and melting in poly(ethylene oxide): Effect of crystal thickness observed in the dynamic heat capacity
T. Albrecht, S. Armbruster, S. Keller and G. StroblFakultät für Physik, Albert-Ludwigs-Universität, 79104 Freiburg, Germany strobl@uni-freiburg.de
(Received 20 April 2001 and Received in final form 13 August 2001)
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.
61.41.+e - Polymers, elastomers, and plastics.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
