Anomalous Segment Diffusion in Polydimethylsiloxane Melts
Anomalous Segment Diffusion in Polydimethylsiloxane Melts
复制标题
聚二甲基硅氧烷熔体中的反常链段扩散
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
B. Geil
中科院分区：
文献类型：
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作者：
S. Pahl;G. Fleischer;F. Fujara;B. Geil
长链聚合物熔体中的链段扩散已通过场梯度核磁共振测量。扩大的数据集和改进的数据分析导致我们对之前发表的 (Macromolecules 1994, 27, 4274) 观点进行了修改。我们现在得出以下结论：在单分散聚二甲基硅氧烷（PDMS）熔体中，中间散射函数的自部分几乎保持高斯分布，即 S(Q,t) ∼ exp[-Q 2 D app (t)t] 对于 t > 5 x 10 -3 s 具有明显的自扩散系数，其时间依赖性在实验精度内与爬行模型一致。长时间自扩散系数 D∞ 的分子量依赖性也是如此。然而，观察到的从异常扩散到长时间扩散的交叉不能在严格的爬行模型中定量地理解。
Segmental diffusion in long-chain polymer melts has been measured by field-gradient NMR. An enlarged set of data and an improved data analysis leads to a modification of our previously published (Macromolecules 1994, 27, 4274) view. We now come to the following conclusions: In monodisperse polydimethylsiloxane (PDMS) melts, the self part of the intermediate scattering function stays almost Gaussian, that is S(Q,t) ∼ exp[-Q 2 D app (t)t] for t > 5 x 10 -3 s with an apparent self-diffusion coefficient whose time dependence is, within experimental accuracy, in accord with the reptation model. This is also the case for the molecular weight dependence of the long-time self-diffusion coefficient D∞. However, the observed cross-over from anomalous to long time diffusion cannot be understood quantitatively within the strict reptation model.