title: Formation of a unique crystal morphology for the poly(ethylene glycol)-poly(epsilon-caprolactone) diblock copolymer.
abstract: The crystallization behaviors of the poly(ethylene glycol)-poly(epsilon-caprolactone) diblock copolymer with the PEG weight fraction of 0.50 (PEG(50)-PCL(50)) was studied by DSC, WAXD, SAXS, and FTIR. A superposed melting point at 58.5 degrees C and a superposed crystallization temperature at 35.4 degrees C were obtained from the DSC profiles running at 10 degrees C/min, whereas the temperature-dependent FTIR measurements during cooling from the melt at 0.2 degrees C/min showed that the PCL crystals formed starting at 48 degrees C while the PEG crystals started at 45 degrees C. The PEG and PCL blocks of the copolymer crystallized separately and formed alternating lamella regions according to the WAXD and SAXS results. The crystal growth of the diblock copolymer was observed by polarized optical microscope (POM). An interesting morphology of the concentric spherulites developed through a unique crystallization behavior. The concentric spherulites were analyzed by in situ microbeam FTIR, and it was determined that the morphologies of the inner and outer portions were mainly determined by the PCL and PEG spherulites, respectively. However, the compositions of the inner and outer portions were equal in the analysis by microbeam FTIR.
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences, Changchun 130022, P. R. China.
authors.forename: Chaoliang
authors.initials: C
authors.lastname: He
authors.forename: Jingru
authors.initials: J
authors.lastname: Sun
authors.forename: Ting
authors.initials: T
authors.lastname: Zhao
authors.forename: Zhongkui
authors.initials: Z
authors.lastname: Hong
authors.forename: Xiuli
authors.initials: X
authors.lastname: Zhuang
authors.forename: Xuesi
authors.initials: X
authors.lastname: Chen
authors.forename: Xiabin
authors.initials: X
authors.lastname: Jing
mesh_terms: D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D008970:Molecular Weight; D011091:Polyesters / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D011091:Polyesters; C016240:polycaprolactone; D011092:Polyethylene Glycols