Coupling of Multiscale Orderings during Flow-Induced Crystallization of Isotactic Polypropylene
Coupling of Multiscale Orderings during Flow-Induced Crystallization of Isotactic Polypropylene
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DOI：
10.1021/acs.macromol.6b02544
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发表时间：
2017-02
期刊：
影响因子：
5.5
通讯作者：
Fengmei Su;Youxin Ji;L. Meng;Zhen Wang;Z. Qi;Jiarui Chang;Jianzhu Ju;Liangbin Li
中科院分区：
文献类型：
--
作者：
Fengmei Su;Youxin Ji;L. Meng;Zhen Wang;Z. Qi;Jiarui Chang;Jianzhu Ju;Liangbin Li
采用原位傅里叶变换红外光谱（FTIR）和同步辐射X射线散射技术研究了部分交联等规聚丙烯（iPP）流动诱导结晶（FIC）过程中链内和链间有序化的顺序和耦合，揭示了在结晶开始前出现的多尺度结构中间体。在施加流动时，首先发生链内构象有序或卷曲-螺旋转变（CHT），这与外部应力直接相关。在大应变下，由于螺旋含量的增加，密度会发生波动，并且足够长的螺旋可能导致FIC之前的取向有序化。结果表明，应力诱导的链内CHT是FIC中必不可少的结构中间体，只要螺旋含量或长度满足相变的标准，它可以进一步与链间取向和密度耦合。我们认为，外部应力，链内共形，
The sequence and coupling of intra- and interchain orderings in flow-induced crystallization (FIC) of partially cross-linked isotactic polypropylene (iPP) is studied with in situ Fourier transform infrared spectroscopy (FTIR) and synchrotron radiation X-ray scattering techniques, which reveal that multiscale structural intermediates emerge prior to the onset of crystallization. Upon imposing flow, intrachain conformational ordering or coil–helix transition (CHT) occurs first, which is directly correlated with external stress. As helical content is built up at large strain, density fluctuation happens, and sufficient long helices may result in orientation ordering before FIC. The results demonstrate that stress induced intrachain CHT is the essential structural intermediate in FIC, which can be further coupled with interchain orientation and density providing either helical content or length meets the criterions for the phase transitions. We propose that coupling among external stress, intrachain conformat...