Study of the Synthesis, Crystallization, and Morphology of Poly(ethylene glycol)-Poly(-caprolactone) Diblock Copolymers
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- 作者：Chaoliang He ; Jingru Sun ; Chao Deng ; Ting Zhao ; Mingxiao Deng ; Xuesi Chen ; and Xiabin Jing
- 刊名：Biomacromolecules
- 出版年：2004
- 出版时间：September 2004
- 年：2004
- 卷：5
- 期：5
- 页码：2042 - 2047
- 全文大小：297K
- 年卷期：v.5,no.5(September 2004)
- ISSN：1526-4602
文摘
Poly(ethylene glycol)-poly(
-caprolactone) diblock copolymers PEG-PCL were synthesized by ring-openingpolymerization of -caprolactone using monomethoxy poly(ethylene glycol) as the macroinitiator and calciumammoniate as the catalyst. Obvious mutual influence between PEG and PCL crystallization was studied byaltering the relative block length. Fixing the length of the PEG block (Mn = 5000) and increasing the lengthof the PCL block, the crystallization temperature of the PCL block rose gradually from 1 to about 35 
Cwhile that of the PEG block dropped from 36 to -6.6 C. Meanwhile, the melting temperature of the PCLblock went up from 30 to 60 C, while that of the PEG block declined from 60 to 41 C. If the PCL blockwas longer than the PEG block, the former would crystallize first when cooling from a molten state and ledto obviously imperfect crystallization of PEG and vice versa. And they both crystallized at the sametemperature, if their weight fractions were equal. We found that the PEG block could still crystallize at-6.6 C even when its weight fraction is only 14%. A unique morphology of concentric spherulites wasobserved for PEG5000-PCL5000. According to their morphology and real-time growth rates, it is concludedthat the central and outer sections in the concentric spherulites were PCL and PEG, respectively, and duringthe formation of the concentric spherulite, the PEG crystallized quickly from the free space of the PCLcrystal at the earlier stage, followed by outgrowing from the PCL spherulites in the direction of right anglesto the circle boundaries until the entire area was occupied.
-caprolactone) diblock copolymers PEG-PCL were synthesized by ring-openingpolymerization of -caprolactone using monomethoxy poly(ethylene glycol) as the macroinitiator and calciumammoniate as the catalyst. Obvious mutual influence between PEG and PCL crystallization was studied byaltering the relative block length. Fixing the length of the PEG block (Mn = 5000) and increasing the lengthof the PCL block, the crystallization temperature of the PCL block rose gradually from 1 to about 35 Cwhile that of the PEG block dropped from 36 to -6.6 C. Meanwhile, the melting temperature of the PCLblock went up from 30 to 60 C, while that of the PEG block declined from 60 to 41 C. If the PCL blockwas longer than the PEG block, the former would crystallize first when cooling from a molten state and ledto obviously imperfect crystallization of PEG and vice versa. And they both crystallized at the sametemperature, if their weight fractions were equal. We found that the PEG block could still crystallize at-6.6 C even when its weight fraction is only 14%. A unique morphology of concentric spherulites wasobserved for PEG5000-PCL5000. According to their morphology and real-time growth rates, it is concludedthat the central and outer sections in the concentric spherulites were PCL and PEG, respectively, and duringthe formation of the concentric spherulite, the PEG crystallized quickly from the free space of the PCLcrystal at the earlier stage, followed by outgrowing from the PCL spherulites in the direction of right anglesto the circle boundaries until the entire area was occupied.