Relations between Stereoregularity and Melt Viscoelasticity of Syndiotactic Polypropylene
Relations between Stereoregularity and Melt Viscoelasticity of Syndiotactic Polypropylene
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DOI：
10.1021/ma401469a
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发表时间：
2013-09
期刊：
影响因子：
5.5
通讯作者：
Naveed Ahmad;R. Girolamo;F. Auriemma;C. Rosa;N. Grizzuti
中科院分区：
文献类型：
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作者：
Naveed Ahmad;R. Girolamo;F. Auriemma;C. Rosa;N. Grizzuti
采用有机金属催化法制备了一系列具有规整度和均匀分布的立体缺陷的间同立构聚丙烯样品，研究了熔体状态下间同立构五单元组浓度与粘弹性平台模量之间的关系。平台模量被发现增加与立构规整度的增加，表明不同的立构规整性的间同立构聚丙烯产生不同的缠结密度的无定形相。平台模量的变化是高度非线性的大值的间同立构五元组的内容，这表明，即使是相对较少的缺陷沿着的间同立构骨架的存在下显着改变的空间填充的态度的聚合物链在熔体中。这一结果证实并扩展了从实验和数值模拟中已经得到的结果，指出了大分子链的动力学在很大程度上受温度控制的概念。
A set of syndiotactic polypropylene samples with tailored degree of stereoregularity and uniform distribution of stereodefects, obtained via organometallic catalysis, was used to study the relation between the syndiotactic pentad concentration and the viscoelastic plateau modulus in the melt state. The plateau modulus was found to increase with increasing the degree of stereoregularity, indicating that syndiotactic polypropylenes of different stereoregularity produce a different entanglement density of the amorphous phase. The change in plateau modulus was highly nonlinear for large values of syndiotactic pentad contents, suggesting that the presence of even a relatively small number of defects along the syndiotactic backbone significantly alters the space filling attitude of the polymer chain in the melt. This result, which confirms and extends those already obtained from experiments and numerical simulations, points out to the concept that the dynamics of macromolecular chains is largely controlled by t...