Polymorphism of Racemic Poly(L-lactide)/Poly(D-lactide) Blend: Effect of Melt and Cold Crystallization
Polymorphism of Racemic Poly(L-lactide)/Poly(D-lactide) Blend: Effect of Melt and Cold Crystallization
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外消旋聚（L-丙交酯）/聚（D-丙交酯）共混物的多晶型：熔融和冷结晶的影响
DOI：
10.1021/jp311878f
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发表时间：
2013-04-04
影响因子：
3.3
通讯作者：
Yang, Ming-Bo
中科院分区：
文献类型：
--
作者：
Bao, Rui-Ying;Yang, Wei;Yang, Ming-Bo
采用差示扫描量热法（DSC）和广角X射线衍射法（WAXD）研究了聚L-乳酸/聚D-乳酸（PLLA/PDLA）共混物的熔融和熔融结晶行为及结晶结构。采用Avrami方程对熔体和冷结晶过程的等温结晶动力学进行了分析。冷结晶的总结晶速率常数（k）远高于熔融结晶。此外，k作为结晶温度的函数在熔融和冷结晶中显示出不同的趋势，表明在熔融和冷结晶中不同的结晶机制。均蒙脱土的多晶型结晶（从δ到α形式的转变结晶温度）不被PLLA和PDLA的等摩尔共混或结晶程序的类型改变，而排他性立体复合物微晶的结晶窗口从熔融结晶的170 ℃加宽到冷结晶的170-200 ℃。在90和100 ℃的结晶温度下，在熔融和冷结晶中均难以形成立构复合物微晶，并且在高于110 ℃的温度下，用于冷结晶的立构复合物微晶的结晶度高于熔融结晶的结晶度。特别地，通过冷结晶可以在170-200 ℃下获得纯的和显著更高结晶度的立体复合物微晶。这些结果为控制立体复合物结晶以扩大其应用提供了巨大的可能性。
The crystallization and melting behaviors and crystalline structure of melt and cold crystallized poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) blend were investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD), respectively. The isothermal crystallization kinetics during the melt and cold crystallization process were analyzed using the Avrami equation. The overall crystallization rate constant (k) of cold crystallization is much higher than that of melt crystallization. Moreover, k as a function of crystallization temperature shows different trends in melt and cold crystallization, indicating different crystallization mechanisms in the melt and cold crystallization. The polymorphic crystallization of homocrystallites (the transition crystallization temperature from delta to alpha form) is not altered by either the equimolar blending of PLLA and PDLA or the type of crystallization procedures, while the crystallization window for exclusive stereocomplex crystallites is widened from 170 degrees C for melt crystallization to 170-200 degrees C for cold crystallization. The stereocomplex crystallites are hard to form in both melt and cold crystallization at crystallization temperatures of 90 and 100 degrees C, and the crystallinity of stereocomplex crystallites for cold crystallization is higher than that of melt crystallization at temperatures above 110 degrees C. Especially, a pure and significantly higher crystallinity of stereocomplex crystallites can be achieved at 170-200 degrees C by cold crystallization. The results provide a huge possibility to control stereocomplex crystallization to enlarge its applications.