TY - JOUR
T1 - Crystallization and structure formation of poly(L-lactide-co-meso-lactide) random copolymers
T2 - A time-resolved wide- and small-angle X-ray scattering study
AU - Cho, Jaedong
AU - Baratian, Stephen
AU - Kim, Jangsoon
AU - Yeh, Fengji
AU - Hsiao, Benjamin S.
AU - Runt, James
N1 - Funding Information:
The Penn State authors would like to express their appreciation to the National Science Foundation (DMR-9900638) and the donors of the ACS Petroleum Research Fund for support of this research. BSH and FY thank a US Department of Energy grant (DEFG0299ER45760) for support of the AP-PRT beamline. We would also like to thank Eric S. Hall of Cargill Dow Polymers for synthesizing the polymers used in this study.
PY - 2002/12/20
Y1 - 2002/12/20
N2 - Time-resolved synchrotron simultaneous wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) experiments were used to investigate the crystallization behavior and microstructure development of poly(L-lactide), PLLA, and two random copolymers containing L-lactide (predominately) and randomly placed R stereochemical defects. The general features of crystallization of PLLA and the copolymers are similar except that the copolymers crystallize much more slowly and to a lesser extent than PLLA, as expected. Lamellar thicknesses derived from SAXS experiments are in very good agreement with mean thicknesses determined in a tapping mode AFM study of the same materials. The reduction in lamellar thickness and crystallinity with increasing meso-lactide content supports significant exclusion of the R stereoisomer from crystalline lamellae. In a separate series of time-resolved WAXD/SAXS experiments, each (co)polymer was crystallized for a fixed time, then heated to above its melting point. The observed behavior suggests a model for crystallization of the copolymers in which thinner lamellae form between 'primary' lamellar stacks during crystallization, with an average lamellar thickness that decreases with increasing R stereoisomer content.
AB - Time-resolved synchrotron simultaneous wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) experiments were used to investigate the crystallization behavior and microstructure development of poly(L-lactide), PLLA, and two random copolymers containing L-lactide (predominately) and randomly placed R stereochemical defects. The general features of crystallization of PLLA and the copolymers are similar except that the copolymers crystallize much more slowly and to a lesser extent than PLLA, as expected. Lamellar thicknesses derived from SAXS experiments are in very good agreement with mean thicknesses determined in a tapping mode AFM study of the same materials. The reduction in lamellar thickness and crystallinity with increasing meso-lactide content supports significant exclusion of the R stereoisomer from crystalline lamellae. In a separate series of time-resolved WAXD/SAXS experiments, each (co)polymer was crystallized for a fixed time, then heated to above its melting point. The observed behavior suggests a model for crystallization of the copolymers in which thinner lamellae form between 'primary' lamellar stacks during crystallization, with an average lamellar thickness that decreases with increasing R stereoisomer content.
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U2 - 10.1016/S0032-3861(02)00823-6
DO - 10.1016/S0032-3861(02)00823-6
M3 - Article
AN - SCOPUS:0037147449
SN - 0032-3861
VL - 44
SP - 711
EP - 717
JO - Polymer
JF - Polymer
IS - 3
ER -