聚丙二醇/二氧化硅复合材料的局域和全局动力学
Local and global dynamics in polypropylene glycol / silica composites
摘要：
采用流变仪、力学谱和介电谱研究了一系列聚丙二醇/二氧化硅纳米复合材料的局部链段动力学和整体动力学。颗粒引起流变学的显著变化，包括变得非牛顿的较高粘度和瞬时剪切粘度中出现应力过冲。然而，没有变化，观察到的平均弛豫时间为段或正常模式动态介电测量。这种不存在颗粒的影响是由于远离颗粒的聚合物链掩蔽了界面响应。当提取未连接的聚合物以隔离界面材料时，测量到弛豫时间的非常大的减少。这种动力学的加速部分是由于界面处的密度降低，大概是束缚链的堆积较差的结果。此外，聚丙二醇链的醚氧的结合截断了正常模式，这将相应的弛豫峰移动到更高的频率。
英文摘要：
The local segmental and global dynamics of a series of polypropylene glycol / silica nanocomposites were studied using rheometry and mechanical and dielectric spectroscopies. The particles cause substantial changes in the rheology, including higher viscosities that become non-Newtonian and the appearance of stress overshoots in the transient shear viscosity. However, no change was observed in the mean relaxation times for either the segmental or normal mode dynamics measured dielectrically. This absence of an effect of the particles is due to masking of the interfacial response by polymer chains remote from the particles. When the unattached polymer was extracted to isolate the interfacial material, very large reductions in the relaxation times were measured. This speeding up of the dynamics is due in part to the reduced density at the interface, presumably a consequence of poorer packing of tethered chains. In addition, binding of the ether oxygens of the polypropylene glycol chains truncates the normal mode, which shifts the corresponding relaxation peak to higher frequencies.
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