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Mesomorphic phase formation of plasticized poly( l ‐lactic acid)
Author(s) -
Koido Shunsuke,
Kawai Takahiko,
Kuroda Shinichi,
Nishida Koji,
Kanaya Toshiji,
Kato Makoto,
Kurose Takashi,
Nakajima Katsuhiko
Publication year - 2014
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.39762
Subject(s) - mesophase , differential scanning calorimetry , materials science , fourier transform infrared spectroscopy , crystallization , recrystallization (geology) , orthorhombic crystal system , polymer chemistry , crystallinity , crystallography , crystal structure , chemical engineering , liquid crystal , composite material , chemistry , organic chemistry , thermodynamics , paleontology , physics , optoelectronics , biology , engineering
ABSTRACT The effects of the crystallization temperature, T c , on the crystal structure as well as its thermal behavior of plasticized poly( l ‐lactic acid) were investigated by means of wide‐angle X‐ray diffraction (WAXD), Fourier‐transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). PLLA blended with succinic acid‐bis[2‐[2‐(2‐methoxyethoxy)ethoxy]ethyl] ester (SAE) showed clear difference in T c dependence of crystalline form compared to PLLA homopolymer. PLLA with 26 wt % SAE crystallized into orthorhombic α form for T c above 80°C, while a peculiar disordered structure (mesophase) was obtained for T c at 40°C. A detailed FTIR analysis of the mesophase of PLLA, focusing on the intra‐ and inter‐chain interaction in the structure, indicated that mesophase had a large degree of disorder in 10/3 helical conformation as well as its packing manner of disordered 10/3 helical chain. Upon heating, mesophase showed a steep exothermic peak at 80°C in DSC thermogram, indicating the phase transformation from mesophase to a form crystal. FTIR results showed that the degree of interchain interaction of C=O in PLLA started to decrease above 60°C, followed by steep increase at 80°C due to the recrystallization into a form. Melt‐recrystallization process in mesophase‐α transformation was clarified. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131 , 39762.