Crystallization behavior and thermal properties of melt-crystallized poly[(R)-3-hydroxybutyric acid-co-6-hydroxyhexanoic acid] films.
Melt-crystallized films of poly[(R)-3-hydroxybutyric acid-co-10mol% 6-hydroxyhexanoic acid] (P[(R)-3HB-co-6HH]) were prepared by isothermal crystallization at various temperatures for 3 days, and subsequently stored at room temperature after the films formed well-developed and volume-filled spherulites. The lamellar morphologies and properties of melt-crystallized films were characterized by means of wide-angle X-ray diffraction, small-angle X-ray scattering, differential scanning calorimetry, transmission electron microscopy, and atomic force microscopy. The melting endotherm of P[(R)-3HB-co-6HH] films was composed of a broad peak starting around room temperature and of a sharper peak starting above the isothermal crystallization temperature. The stacking of flat-on lamellae with lamellar periodicity of 8-10 nm was detected on the surface of P[(R)-3HB-co6HH] films after the primary crystallization at 110 degrees C. On storage at room temperature above the Tg (-5 degrees C) of copolyester, thin crystals of 1-4 nm thickness appeared on the surface of P[(R)-3HB-co-6HH] films crystallized at 110 degrees C. These results suggest that long sequences of (R)-3HB units in a random copolyester form relatively thick P[(R)-3HB] crystalline lamellae during the primary crystallization process at a given crystallization temperature, while shorter sequences of (R)-3HB units, which are incapable of crystallizing at a given crystallization temperature, form relatively thin crystalline lamellae during the subsequent crystallization process at room temperature.
Abe
H
H
Polymer Chemistry Laboratory, The Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
Kikkawa
Y
Y
Aoki
H
H
Akehata
T
T
Iwata
T
T
Doi
Y
Y
D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D018360:Crystallography, X-Ray; D006885:Hydroxybutyrates / Q000737:chemistry*; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D011091:Polyesters / Q000737:chemistry*; D013816:Thermodynamics; D013997:Time Factors; D000094122:Polyhydroxybutyrates
D006885:Hydroxybutyrates; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates