Effect of the different architectures and molecular weights on stereocomplex in enantiomeric polylactides-b-MPEG block copolymers

Publication date: 11 August 2017
Source:Polymer, Volume 123
Author(s): Dongdong Zhou, Jun Shao, Jingru Sun, Xinchao Bian, Sheng Xiang, Gao Li, Xuesi Chen
Poly(lactide) stereocomplex (PLA SC) and poly(ethylene glycol) (PEG) crystallites were obtained in MPEG-b-PLLA/MPEG-b-PDLA (linear blend, 1/1) and 4PEG-b-PLLA/4PEG-b-PDLA (4-arm blend, 1/1) by solution-casting method. The molecular weights of PLLA and PDLA (Mn, PLA) were similar in all the linear and 4-arm blends. Only PLA SC and PEG crystallites were observed, and PLA homocrystallites were absent in all blends. The different Mn, PLA and chain architectures did not alter the crystalline structures of PLA SC and PEG, but greatly influenced their melting temperatures and crystallinities. As the average Mn, PLA per arm of linear and 4-arm blends were similar, the melting temperatures and crystallinities of PLA SC and PEG in 4-arm blends were always lower than those of linear blends, which could be ascribed to the huge steric hindrance of 4-arm structures. This investigation on PEG-b-PLLA/PEG-b-PDLA blends with various structures could provide basic data for the applications of PLA stereocomplex.

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