Morphology of a highly asymmetric double crystallizable poly(epsilon-caprolactone-b-ethylene oxide) block copolymer.
The morphology of a highly asymmetric double crystallizable poly(epsilon-caprolactone-b-ethylene oxide) (PCL-b-PEO) block copolymer has been studied with in situ simultaneously small and wide-angle x-ray scattering as well as atomic force microscopy. The molecular masses Mn of the PCL and PEO blocks are 24,000 and 5800, respectively. X-ray scattering and rheological measurements indicate that no microphase separation occurs in the melt. Decreasing the temperature simultaneously triggers off a crystallization of PCL and microphase separation between the PCL and PEO blocks. Coupling and competition between microphase separation and crystallization results in a morphology of PEO spheres surrounded by PCL partially crystallized in lamella. Further decreasing temperature induces the crystallization of PEO spheres, which have a preferred orientation due to the confinements from hard PCL crystalline lamella and from soft amorphous PCL segments in different sides. The final morphology of this highly asymmetric block copolymer is similar to the granular morphology reported for syndiotactic polypropylene and other (co-) polymers. This implies a similar underlying mechanism of coupling and competition of various phase transitions, which is worth further exploration.
Li
Liangbin
L
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Anhui 230026, China. lbli@ustc.edu.cn
Meng
Fenghua
F
Zhong
Zhiyuan
Z
Byelov
Dmytro
D
de Jeu
Wim H
WH
Feijen
Jan
J
D001672:Biocompatible Materials / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D044367:Phase Transition; D011091:Polyesters / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D014961:X-Ray Diffraction
D001672:Biocompatible Materials; D011091:Polyesters; C492324:poly(epsilon-caprolactone)-poly(oxyethylene)-poly(epsilon-caprolactone); D011092:Polyethylene Glycols