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Effects of Molecular Weight on the Crystallization and Melting Behaviors of Poly(L-lactide)
In this study, a series of monodispersed poly(L-lactide)(PLLA) were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight(Mn) on the crystallization and melting behaviors of PLLA were investigated by differential sca...
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Published in: | 高分子科学:英文版 2016 (1), p.69-76 |
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Main Author: | |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | In this study, a series of monodispersed poly(L-lactide)(PLLA) were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight(Mn) on the crystallization and melting behaviors of PLLA were investigated by differential scanning calorimetry(DSC) and wide-angle X-ray diffraction(WAXD). The total crystallization rate of PLLA was Mn-dependent, which reached the maximum value for PLLA with Mn of 18.6 kg/mol. In addition, when Mn of PLLA was 18.6 kg/mol, the melting enthalpy(ΔHm) showed a maximum value(87.1 J/g), which was the highest reported value till now. The critical temperature for change of crystal formation from ?-form to ?-form crystals increased in the isothermal crystallization process with Mn increasing. In the reheating procedure, high-Mn PLLA demonstrated a small exothermal peak prior to the dominant melting peak, corresponding to crystal transition from ?- to ?-form, but low-Mn PLLA didn't show the peak of crystal transition. These different crystallization and melting behaviors were attributed to the different chain mobility of PLLA with different Mn. |
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ISSN: | 0256-7679 1439-6203 |