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Time-Resolved Isothermal Crystallization of Absorbable PGA-co-PLA Copolymer by Synchrotron Small-Angle X-Ray Scattering and Wide-Angle X-Ray Diffraction

Published

Author(s)

Z G. Wang, X H. Wang, B S. Hsiao, S Andjelic, D Jamiolkowski, J McDivitt, J Fischer, J Zhou, Charles C. Han

Abstract

The isothermal crystallization behavior of absorbable dyed and undyed PGA-co-PLA copolymers was investigated by time-resolved simultaneous synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) methods. The morphological parameters extracted from time-resolved SAXS profiles show that long period and lamellar thickness decrease slightly after the very early stages of the primary crystallization. The unit cell parameters a and b and the apparent lateral crystal sizes L110 and L020 have been extracted from the corresponding WAXD profiles. A significant decrease in unit cell parameters and a substantial increase in the apparent crystal sizes are seen during the initial crystallization stage. Both SAXS (the scattering invariant, Q) and WAXD (the crystallinity, Xc) demonstrate that the crystallization rate is the fastest at 130 degrees C. These copolymers show a bell-shape crystallization rate curve with respect to temperature, where the dyed PGA-co-PLA copolymer has a faster crystallization rate than the undyed material even though the inclusion of the low molecular weight organic dye is very small (0.2% by weight). We conclude that the dye molecule, which enhances the visibility during surgery, act as a nucleating agent to increase the overall crystallization rate. Even though the crystallization rate is much slower at 90 degrees C than that at 130 degrees C, the long period and lamellar thickness formed at 90 degrees C are lower than those formed at higher temperatures. The dyed and undyed PGA-co-PLA copolymers have almost the same morphological parameters at the same temperature, but have very different drystallization rates. This indicates that the morphological parametes of the lamellar structures in the polymers depend primarily on the crystallization temperature rather than the crystallization rate. It is evident that the thermodynamic factor driven by the temperature determines the lamellar morphology. The final unit cell parameters a and b and the final apparent crystal sizes all increase with temperature, indicating that crystal perfection prevails at high temperature.
Citation
Polymer
Volume
42
Issue
No. 21

Keywords

PGA-co-PLA, synchrontron small angle x-ray scatterin, time-resolved isothermal crystallization, unit cell parameters, wide angle x-ray diffraction

Citation

Wang, Z. , Wang, X. , Hsiao, B. , Andjelic, S. , Jamiolkowski, D. , McDivitt, J. , Fischer, J. , Zhou, J. and Han, C. (2001), Time-Resolved Isothermal Crystallization of Absorbable PGA-co-PLA Copolymer by Synchrotron Small-Angle X-Ray Scattering and Wide-Angle X-Ray Diffraction, Polymer, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851896 (Accessed May 21, 2024)

Issues

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Created September 30, 2001, Updated October 12, 2021