Low frequency NMR relaxometry for the study of polymer dynamics

我们计划结合联合收割机场循环（FC）-和场梯度（FG）-NMR研究线性聚合物熔体的集体动力学。将系统地利用第一个供资期的工具性成就。例如，频率相关弛豫速率现在覆盖从40 MHz下至约300 Hz的范围。对于其他聚合物系统，应进一步检查管道蠕动模型缺陷的提示，并考虑聚合物动力学的替代模型。此外，我们的FC数据，双量子NMR数据（K。Saalwächter，Halle）和通用模拟进行分析。总的目标是找出在何种程度上的管道爬行模型保持其有效性在微观水平。我们计划开始测量的纯重取向动力学寻找第一个系统的2 H弛豫色散。这些实验将补充从1H/2 H稀释实验中提取的链内1H弛豫速率分散和链间速率分散的测定。两者的相对贡献提供了有价值的信息的微观动力学，并允许区分不同的聚合物模型。从利率，我们将推导出均方位移（MSD）和联合收割机这些结果与直接测量FG数据。通过这种方式，我们能够，第一次，以涵盖整个次扩散制度的MSD。对于理论部分，我们已经获得了N教授。Fatkullin（喀山）作为一个同事。此外，仪器的发展将进一步推进。我们将尝试常规地达到远低于100 Hz的1H频率，这比商业机器的频率低两个数量级以上。有了如此宽的频率跨度，我们可以真正考虑FC弛豫作为一个强大的分子流变学方法研究不同的软物质系统。

We plan to combine field-cycling (FC)- and field-gradient (FG)-NMR for studying the collective dynamics of linear polymer melts. The instrumental achievements of the first funding period will be used in a systematic way. For instance, the frequency dependent relaxation rate now covers a range from 40 MHz down to about 300Hz. Hints for deficiencies of the tube-reptation model shall be further examined for other polymer systems, and alternative models for the polymer dynamics will be considered. Further, discrepancies between our FC data, double quantum NMR data (K. Saalwächter, Halle) and generic simulations will be analyzed. The overall goal is to find out to which extent the tube-reptation model keeps its validity at a microscopic level. We plan to start measurements of the pure reorientation dynamics by looking for the first systematically at the 2H relaxation dispersion. These experiments will complement the determination of the intrachain 1H relaxation rate dispersion and the interchain rate dispersion, extracted from 1H/2H dilution experiments. The relative contribution of both provides valuable information on the microscopic dynamics and allows discriminating different polymer models. From the inter rate we will deduce the mean squared displacement (MSD) and combine these results with directly measured FG data. In this way we are able, for the first time, to cover the whole sub-diffusive regime in terms of the MSD. For the theory part we have gained Prof. N. Fatkullin (Kazan) as a coworker. Also, the instrumental development will be further pushed forward. We will try to reach down to 1H frequencies well below 100 Hz routinely, which is more than two orders of magnitude below those of commercial machines. With such a wide frequency span we can truly consider FC relaxometry as a powerful molecular rheology method for studying diverse soft matter systems.