Polymeric Interphases in Self-Ordered Porous Alumina: NMR Investigations of the Chain Dynamics

采用固体核磁共振研究了硬中性或吸引壁对熔体中聚合物链动力学的纳米约束效应。我们应用各种核磁共振技术来表征和阐明基于自有序纳米多孔氧化铝的真实模型复合材料的链动力学，具有明确的几何形状和调整无机表面性质的可能性。与其他项目密切合作，采用中子散射、场循环核磁共振和计算机模拟，我们专注于局部分段模式以及更大规模的重复运动，特别强调它们的各向异性。在第一个资助期，我们发现在靠近弱相互作用壁的几nm的层中，纠缠熔体的长期动力学与体体有明显的不同，并且具有相当的各向异性，并且这种效应与纠缠间距呈比例关系。进一步的初步研究表明，这些影响与取向有关，并且也发生在名义上未纠缠的熔体中。利用脉冲梯度核磁共振和共聚焦荧光显微镜研究了大尺度扩散和渗透动力学，并成功进行了首次孔壁修饰实验。在第二个资助期，我们计划通过比较不同纠缠间距的聚合物来扩展初始研究，重点研究孔壁极性对动力学的影响，通过角度相关实验对效应的各向异性进行定量理解，最后实施自旋扩散实验来研究性能梯度。

The nanoscopic confinement effect of hard neutral or attractive walls on the dynamics of polymer chains in the melt is studied by solid-state NMR. We apply a variety of NMR techniques to the characterization and the elucidation of chain dynamics in true model composites based on self-ordered nanoporous alumina with well-defined geometry and the possibility to tune the properties of the inorganic surface. In close collaboration with other projects employing neutron scattering, field-cycling NMR, and computer simulations , we focus on the local segmental modes as well as on larger-scale reptation motions, with particular emphasis on their anisotropy. In the first funding period, we found that the long-time dynamics of entangled melts is significantly different from the bulk and rather anisotropic in a layer of a few nm close to the weakly interacting wall, and that the effect appears to scale with the entanglement spacing. Further preliminary studies demonstrated that these effects are orientation dependent, and also occur for nominally unentangled melts. We also studied the large-scale diffusion by pulsed-gradient NMR and the infiltration kinetics by confocal fluorescence microscopy, and successfully conducted first pore-wall modification experiments. For the second funding period, we plan to extend the initial studies by comparing polymers with different entanglement spacings, focus at the effects of pore-wall polarity on the dynamics, develop a quantitative understanding of the anisotropy of the effects via angle-dependent experiments, and finally implement spin-diffusion experiments to study property gradients.