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Stabilization of Nuclei of Lamellar Polymer Crystals: Insights from a Comparison of the Hoffman–Weeks Line with the Crystallization Line
journal contribution
posted on 2016-03-10, 19:18 authored by Jun Xu, Barbara Heck, Hai-Mu Ye, Jing Jiang, Yi-Ren Tang, Jin Liu, Bao-Hua Guo, Renate Reiter, Dong-Shan Zhou, Günter ReiterWe have studied melting of poly(butylene
succinate), isothermally
crystallized over a wide temperature range, employing a combination
of the Hoffman–Weeks plot and the Gibbs–Thomson crystallization
line, determined by small-angle X-ray scattering measurements. A change
in the slope α of the Hoffman–Weeks
(H–W) line, accompanied by a change of the slope of the crystallization
line, was observed for crystallization temperatures higher than 110
°C. α was reaching a value
of 1, implying that no intersection point between the H–W line
and the Tm = Tc line could be obtained. (Tm is the measured melting temperature
and Tc is the temperature
at which the sample was crystallized). This observation was corroborated
by the crystallization line, which was found to be parallel to the
melting line for Tc >
110 °C. We relate these changes in slope to different stabilization
mechanisms of the secondary nuclei at the growth front of polymer
lamellar crystals. For Tc > 110 °C, secondary nuclei are proposed to be stabilized
by
coalescence of neighboring nuclei, all having a small width. By contrast,
for Tc > 110 °C,
the number density of secondary nuclei is low and thus their coalescence
is rare. Accordingly, nuclei are stabilized by growing in size, mainly
increasing their width.