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The difference of equilibrium melting point between poly( l ‐lactic acid) and poly( l ‐lactic acid)/poly( d ‐lactic acid) blends: cases with three molecular weights
Author(s) -
Guo Weijie,
Shao Jun,
Ye Xinxin,
Sun Peng,
Meng Chunfeng,
Li Zhaolei,
Zheng Zhiping,
Yan Chao
Publication year - 2019
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.5607
Subject(s) - lactic acid , melting point , crystallization , supercooling , materials science , melting temperature , molecular mass , polymer chemistry , crystallography , chemistry , thermodynamics , organic chemistry , bacteria , biology , composite material , physics , genetics , enzyme
In order to explore the origin of the higher melting point of poly(lactic acid) (PLA) stereocomplex crystal (SC) than that of homo‐crystal (HC), the equilibrium melting point ( T m 0 ) differential between SC and HC was determined using the Hoffman–Weeks method. The results showed that, for PLA samples with M n around 16, 20 and 65 kg mol −1 , the T m 0 differential between SC and HC is around 36, 42 and 55 °C, respectively. Thus, the higher melting point of SC compared to HC does not stem from T m 0 differential only. For PLA samples with lower M n , the supercooling differential between poly( l ‐lactic acid) (PLLA)/poly( d ‐lactic acid) (PDLA) blends and PLLA is smaller than that with higher M n , which means chain diffusion behavior is crucial for SC formation in PLLA/PDLA blends. The fact that the SC adopts the intermolecular parallel arrangement rather than the adjacent chain folding is verified by the greater slope of the melting point of SC versus crystallization temperature fitting curve when M n is relative higher. © 2018 Society of Chemical Industry