Banded spherulitic structures of poly(ethylene adipate), poly(butylene succinate) and in their blends.
Banded spherulitic structures of poly(ethylene adipate), poly(butylene succinate) and in their blends.
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DOI：
10.1039/b817597g
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发表时间：
2009-02
期刊：
影响因子：
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通讯作者：
Tianchang Wang;Haijun Wang;Huihui Li;Z. Gan;Shouke Yan
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文献类型：
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作者：
Tianchang Wang;Haijun Wang;Huihui Li;Z. Gan;Shouke Yan
用光学显微镜和原子力显微镜研究了PEA、PBS及其共混物的带状球晶。结果表明，在23℃~ 36℃的温度范围内，PEA形成规则的带状结构，否则只观察到马尔氏交叉球晶。带状PEA球晶呈现双环特征，两个等效双折射环之间的带间距随温度的升高而增大。PEA带状球晶中的环消光是由片层扭转引起的。在一个扭转周期内存在两个等效位置，不存在双折射现象。PBS也可以在环带状球晶中生长，在宽的温度窗内，形成带状结构的高温阈值并不明显，如PEA的情况。纯PBS球晶的双环特征也不明显。发现PBS与PEA共混有利于PBS带状结构的形成。在结晶过程中，在75℃下，早期生长的PBS球晶表现出弱双折射，具有明显的环带状结构。0℃下PEA的结晶对初始双折射环的双折射增量有很大贡献。这是由原子力显微镜观察发现的基于层间相分离的PBS和PEA的类似晶体取向引起的。发现PBS球晶的能带间距随温度的升高和PEA含量的增加而增大。这源于PBS的链迁移率随温度和PEA组分的加入而增加。
Banded spherulites of PEA, PBS and their PBS-PEA blends were studied by optical and atomic force microscopies. It was found that PEA forms a regular banded structure within the temperature range 23 degrees C to 36 degrees C, otherwise only Maltese-cross spherulites are observed. The banded PEA spherulites exhibit a double ring feature with band spacing between two equivalent birefringent rings increasing with temperature. The ring extinction in PEA banded spherulites is caused by a lamellar twist. There exist two equivalent positions in one twisting period, which show no birefringence. The PBS can also grow in ring-banded spherulites in a wide temperature window with the high temperature threshold for forming banded structures that are not sharply delineated, as in the case of PEA. Also the double ring feature is not so pronounced for the spherulites of pure PBS. Blending PBS with PEA is found to favor the formation of PBS banded structures. During the crystallization process, the early growing PBS spherulites at 75 degrees C show weak birefringence with an evident ring-banded structure. The crystallization of PEA at 0 degrees C makes a great contribution to the birefringence increment of the initially-birefringent rings. This is caused by the analogic crystal orientation of PBS and PEA based on interlamellar phase separation as revealed by AFM observation. The band spacing of PBS spherulites is found to be increase with both increasing temperature and increasing PEA content. This stems from an increment in chain mobility of PBS both with temperature and addition of the PEA component.