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標題: Crystallization-induced orientation for microstructures of poly(L-lactide)-b-poly(epsilon-caprolactone) diblock copolymers
作者: Ho, R.M.
Hsieh, P.Y.
Tseng, W.H.
Lin, C.C.
Huang, B.H.
Lotz, B.
關鍵字: in-vitro degradation;order-disorder transition;to-lamellar transition;epitaxial crystallization;thin-films;microdomain orientation;block-copolymers;aliphatic polyesters;electric-fields;benzoic-acid
Project: Macromolecules
期刊/報告no:: Macromolecules, Volume 36, Issue 24, Page(s) 9085-9092.
The formation of large-sized, well-oriented microdomains Of poly(L-lactide)-b-poly(epsilon-caprolactone) (PLLA-PCL) was successfully achieved by using different crystalline substrates including benzoic acid (BA) and hexamethylbenzene, (HMB), whereas spherulitic crystalline texture was obtained on amorphous substrates. Crystallization-induced orientation of PLLA-PCL microstructures is attributed to directional crystallization of eutectic type between crystalline PLLA and substrate, regardless of microphase separation. Surprisingly, a flat-on crystalline morphology (i.e., with the chain axis normal to the substrate) was obtained, as evidenced by single-crystal-like [001] zonal electron diffraction (ED). By contrast, an edge-on crystalline morphology (i.e., with the chain axis parallel to the substrate) was observed for PLLA homopolymer under the same condition. The crystallographic organization of PLLA-PCL microdomains as observed by transmission electron microscopy, ED, and scanning probe microscopy suggests that the growth direction of PLLA crystals is along the alpha-axis direction, which suggests that the growth direction of PLLA crystals is along the alpha-axis direction that corresponds well with the preferential growth direction (i.e., b-axis direction) of BA or HMB crystals. As a result, the phase-separated lamellar morphology consists of an alternation of a flat-on layer of PLLA lamellae and of an amorphous layer of PLLA and PCL components.
ISSN: 0024-9297
DOI: 10.1021/ma0347868
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