Investigation of phase transitional behavior of poly(L-lactide)/poly(D-lactide) blend used to prepare the highly-oriented stereocomplex
Investigation of phase transitional behavior of poly(L-lactide)/poly(D-lactide) blend used to prepare the highly-oriented stereocomplex
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DOI：
10.1021/ma061693s
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发表时间：
2007-02-20
期刊：
影响因子：
5.5
通讯作者：
Domb, Abraham J.
中科院分区：
文献类型：
--
作者：
Zhang, Jianming;Tashiro, Kohji;Domb, Abraham J.
通过使用高分子量PLLA和中分子量PDLA物种的高度取向的1：1化学计量比共混物，并通过选择合适的退火条件，我们已经成功地首次观察到在加热和冷却过程中的相变现象，通过测量的X射线纤维图和偏振红外光谱的温度依赖性。发现拉制样品由两种晶相组成;无序α形式（α '）和立体复合物（β（c））。在加热过程中，发现α '形式在120摄氏度以上重组为取向的α相，其在180摄氏度左右熔化。然而，通过进一步加热该样品，发现部分熔融链在具有高度链取向的β（c）微晶表面上结晶。在随后从β（c）相冷却的过程中，未取向的α晶体在约120 ℃出现，并与高度取向的β（c）晶体共存。
By using the highly oriented 1:1 stoichiometric blend of high-molecular-weight PLLA and middle-molecular-weight PDLA species and by choosing a suitable annealing condition, we have succeeded for the first time to observe the phase transition phenomenon in the heating and cooling processes by measuring the temperature dependence of the X-ray fiber diagram and polarized IR spectra. The as-drawn sample was found to consist of the two crystalline phases; disordered alpha form (alpha') and stereocomplex (beta(c)). In the heating process, the alpha' form was found to be reorganized into the oriented alpha phase above 120 degrees C, which melted around 180 degrees C. However, by heating this sample some more, some parts of the molten chains are found to crystallize on the surface of the beta(c) crystallites with high degree of chain orientation. In the subsequent cooling process from the beta(c) phase, the unoriented alpha crystal appeared at around 120 degrees C and coexisted with the highly oriented beta(c) crystals.