English

Influence of Chain Architectures on Crystallization Behaviors of PLLA Block in PEG/PLLA Block Copolymers

• Sheng Xiang ^1,2,3, ,
• Dong-Dong Zhou ^4, ,
• Li-Dong Feng ^1,2, ,
• Xin-Chao Bian ^1,2, ,
• Gao Li ^{1,2, ,} ,
• Xue-Si Chen ^{1,2, ,} ,
• Tian-Chang Wang ^1,2,

• a.

  Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China

• b.

  Jilin Biomedical Polymers Engineering Laboratory, Changchun 130022, China

• c.

  University of Chinese Academy of Sciences, Beijing 100049, China

• d.

  South China Advanced Institute for Soft Matter Science and Technology, South China University of Technology, Guangzhou 510640, China

Corresponding author: Gao Li, ligao@ciac.ac.cn Xue-Si Chen, xschen@ciac.ac.cn

• Received Date: 08 October 2018
  Accepted Date: 28 November 2018
  Revised Date: 26 November 2018
  Available Online: 01 March 2019

Abstract: The effect of the architecture of poly(ethylene glycol)/poly(L-lactide) (PEG/PLLA) block copolymers on the non-isothermal crystallization behaviors of PLLA blocks was investigated by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). 1-Arm MPEG-b-PLLA and 4-arm PEG-b-PLLA (4PEG-b-PLLA) were synthesized by the ring-opening polymerization of L-lactide in the presence of poly(ethylene glycol) methyl ether (MPEG) and 4-arm poly(ethylene glycol) (4PEG). 4-Arm PLLA-b-MPEG (4PLLA-b-PEG) was synthesized by coupling 4-arm PLLA and MPEG. The WAXD results indicated that the crystalline structure of PLLA blocks did not alter due to the different chain architectures. The average values of Avrami index ( ) were all above 4, which indicated that the nucleation mechanism of PLLA blocks was heterogeneous nucleation, regardless of the architectures. The overall crystallization rates were decreased markedly as following: MPEG-b-PLLA > 4PEG- b-PLLA > 4PLLA- b-PEG, ascribed to the different confinement by PEG blocks and to the steric hindrance of chain architectures. Therefore, the crystallization of PLLA blocks became more difficult and the crystallization activation energy of the PLLA blocks increased due to the confinement of chain architectures.

Key words:
• Poly(L-lactide)
•  /  Poly(ethylene glycol)/poly(L-lactide) block copolymer
•  /  Non-isothermal crystallization
•  /  Chain architecture

• 
  
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