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Structural changes in isothermal crystallization processes of synthetic polymers studied by time-resolved measurements of synchrotron-sourced X-ray scatterings and vibrational spectra

Structural changes in isothermal crystallization processes of synthetic polymers studied by... Abstract The structural changes occurring in the isothermal crystallization processes of polyethylene (PE), polyoxymethylene (POM), and vinylidene fluoridetrifluoroethylene (VDFTrFE) copolymer have been reviewed on the basis of our recent experimental data collected by the time-resolved measurements of synchrotron-sourced wide-angle (WAXS) and small-angle X-ray scatterings (SAXS) and infrared spectra. The temperature jump from the melt to a crystallization temperature could be measured at a cooling rate of 600–1,000°C/min, during which we collected the WAXS, SAXS, and infrared spectral data successfully at time intervals of ca. 10 sec. In the case of PE, the infrared spectral data clarified the generation of chain segments of partially disordered trans conformations immediately after the jump. These segments then became transformed into more-regular all-trans-zigzag forms, followed by the formation of an orthorhombic crystal lattice. At this stage, the generation of a stacked lamellar structure having an 800-Å-long period was detected in the SAXS data. This structure was found to transfer successively to a more densely packed lamellar structure having a 400-Å-long period as a result of the secondary crystallization of the amorphous region in-between the original lamellae. As for POM, the formation process of a stacked lamellar structure was essentially the same as that mentioned above for PE, as evidenced from the analysis of SAXS and WAXS data. The observation of morphology-sensitive infrared bands revealed the evolution of fully extended helical chains after the generation of lamellae having folded chain structures. We speculate that these extended chains exist as taut tie chains passing continuously through the neighboring lamellae. In the isothermal crystallization of VDFTrFE copolymer from the melt, a paraelectric high-temperature phase was detected at first and then it transferred into the ferroelectric low-temperature phase at a later stage. By analyzing the reflection profile of the WAXS data, the structural ordering in the high-temperature phase and the ferroelectric phase transition to the low-temperature phase of the multidomain structure were traced successfully. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png "Macromolecular Research" Springer Journals

Structural changes in isothermal crystallization processes of synthetic polymers studied by time-resolved measurements of synchrotron-sourced X-ray scatterings and vibrational spectra

Tashiro, Kohji; Hama, Hisakatsu
"Macromolecular Research" , Volume 12 (1): 10 – Feb 1, 2004
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References (15)

Publisher
Springer Journals
Copyright
2004 The Polymer Society of Korea and Springer
ISSN
1598-5032
eISSN
2092-7673
DOI
10.1007/BF03218988
Publisher site
See Article on Publisher Site

Abstract

Abstract The structural changes occurring in the isothermal crystallization processes of polyethylene (PE), polyoxymethylene (POM), and vinylidene fluoridetrifluoroethylene (VDFTrFE) copolymer have been reviewed on the basis of our recent experimental data collected by the time-resolved measurements of synchrotron-sourced wide-angle (WAXS) and small-angle X-ray scatterings (SAXS) and infrared spectra. The temperature jump from the melt to a crystallization temperature could be measured at a cooling rate of 600–1,000°C/min, during which we collected the WAXS, SAXS, and infrared spectral data successfully at time intervals of ca. 10 sec. In the case of PE, the infrared spectral data clarified the generation of chain segments of partially disordered trans conformations immediately after the jump. These segments then became transformed into more-regular all-trans-zigzag forms, followed by the formation of an orthorhombic crystal lattice. At this stage, the generation of a stacked lamellar structure having an 800-Å-long period was detected in the SAXS data. This structure was found to transfer successively to a more densely packed lamellar structure having a 400-Å-long period as a result of the secondary crystallization of the amorphous region in-between the original lamellae. As for POM, the formation process of a stacked lamellar structure was essentially the same as that mentioned above for PE, as evidenced from the analysis of SAXS and WAXS data. The observation of morphology-sensitive infrared bands revealed the evolution of fully extended helical chains after the generation of lamellae having folded chain structures. We speculate that these extended chains exist as taut tie chains passing continuously through the neighboring lamellae. In the isothermal crystallization of VDFTrFE copolymer from the melt, a paraelectric high-temperature phase was detected at first and then it transferred into the ferroelectric low-temperature phase at a later stage. By analyzing the reflection profile of the WAXS data, the structural ordering in the high-temperature phase and the ferroelectric phase transition to the low-temperature phase of the multidomain structure were traced successfully.

Journal

"Macromolecular Research" – Springer Journals

Published: Feb 1, 2004

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