Crystallization and Melting Behavior of Poly (L-lactic Acid)

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• 作者：Takahiko Kawai ; Nelly Rahman ; Go Matsuba ; Koji Nishida ; Toshiji Kanaya ; Mitsuru Nakano ; Hirotaka Okamoto ; Jumpei Kawada ; Arimitsu Usuki ; Nobutaka Honma ; Katsuhiko Nakajima ; Masatoshi Matsuda
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：December 25, 2007
• 年：2007
• 卷：40
• 期：26
• 页码：9463 - 9469
• 全文大小：289K
• 年卷期：v.40,no.26(December 25, 2007)
• ISSN：1520-5835

文摘

Effects of the crystallization temperature on the crystal structure and its melting behavior of poly(L-lactic acid) (PLLA) have been investigated by means of wide-angle (WAXS) and small-angle (SAXS) X-rayscattering, optical microscopy, and differential scanning calorimetory (DSC). PLLA was found to crystallize asthe form when the crystallization temperature T_c was higher than 120 C, while significant change in latticeparameters was seen for T_c's below 120 C. The ratio of the a- and b-axis lengths begins to decrease with T_cbelow 120 C and is 3^1/2 below 90 C, which suggests a new crystalline form with hexagonal packing, namely,the ' form. The possible reason for ' formation is discussed. High-temperature WAXS and SAXS measurementsshowed that ' crystal transforms into ordered a form during heating. The transition takes place at 150 C withouta decrease in scattering intensity and without heating rate dependence. The mechanism for the transition is discussed.