Molecular origin of demixing, prior to crystallization, of atactic polypropylene/isotactic polypropylene blends upon cooling from the melt.
Molecular origin of demixing, prior to crystallization, of atactic polypropylene/isotactic polypropylene blends upon cooling from the melt.
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DOI：
10.1063/1.1795712
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发表时间：
2004-10
期刊：
影响因子：
--
通讯作者：
Phillip Choi;W. Mattice
中科院分区：
文献类型：
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作者：
Phillip Choi;W. Mattice
采用次近邻钻石晶格和三态旋转等长态模型，对125℃下无定形50/50无规聚丙烯(APP)/等规聚丙烯(IPP)混合物进行了数值模拟。结果表明，在与大气压力相对应的类液体密度下，APP更喜欢与其他APP链相互作用，而不是与IPP链相互作用。这一结果与Keith和Padden的推论是一致的。太棒了。35,1286(1964)]在IPP开始结晶之前，APP和IPP在125摄氏度的熔融中倾向于彼此分离。无定形APP/IPP共混物的不相容倾向可能归因于采用全反式构象的APP链中存在短的间规序列。在125℃时，这对这样的子链之间具有吸引力的分子间相互作用促进了APP和IPP的分离。这种相互作用在较高的温度下被削弱，此时APP和IPP变得相容。结果还表明，共混物的相容性随着压力的增加而增加。然而，压力效应的来源尚不清楚。
An amorphous 50/50 atactic polypropylene (aPP)/isotactic polypropylene (iPP) mixture at 125 degrees C was simulated using a second nearest neighbor diamond lattice and a three states rotational isometric state model. The result suggests that at the liquidlike density that corresponds to the atmospheric pressure, aPP prefers to interact with other aPP chains rather than with iPP chains. The result is consistent with the inference of Keith and Padden [J. Appl. Phys. 35, 1286 (1964)] that aPP and iPP will tend to separate from one another in their melt at 125 degrees C, before the onset of crystallization of iPP. The tendency for immiscibility of the amorphous aPP/iPP blend is likely attributed to the presence of short syndiotactic sequences in the aPP chains adopting all-trans conformations. The attractive intermolecular interaction of pairs of such subchains at 125 degrees C promotes the separation of aPP from iPP. This interaction is weakened at higher temperature, where aPP and iPP become miscible. The result also shows that miscibility of the blend increases with increasing pressure. However, the origin of the pressure effect is not clear.