期刊
POLYMER
卷 44, 期 3, 页码 711-717出版社
ELSEVIER SCI LTD
DOI: 10.1016/S0032-3861(02)00823-6
关键词
crystallization; polylactides; random copolymers
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 stereoisorner 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. (C) 2002 Elsevier Science Ltd. All rights reserved.
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