先进固体NMR技术研究高分子结构与动力学

Applications of Advanced Solid-State NMR Techniques in Studying the Structure and Dynamics of Polymers

随着固体NMR理论和谱仪硬件技术的不断发展,近年来固体NMR技术在高分子多尺度结构与动力学研究领域中正发挥着越来越重要的作用.多脉冲及高速魔角旋转(MAS)等质子高分辨技术的发展使得高灵敏度的1 H谱可有效地用于高分子化学结构与链间相互作用的检测;基于化学键(J耦合)相关和通过空间(偶极耦合)相互作用的各种二维异核相关谱NMR新技术,使得复杂高分子的链结构得以严格解析.基于MAS下同核和异核偶极-偶极相互作用、化学位移各向异性等各向异性相互作用重聚的系列新技术,使得研究者可在采用高分辨1 H或13 C检测信号的同时检测准静态下的各向异性相互作用,进而获得与之密切相关的结构和动力学信息.通过质子偶极滤波技术可有效检测多相聚合物中的界面相与相区尺寸、高分子共混物中的相容性等问题.在动力学的研究中,通过质子间自旋扩散的有效压制技术和化学位移各向异性的重聚,目前已经可以有效地获取链段上单个化学键的快速局域运动以及链段的超慢分子运动.上述丰富的多尺度NMR技术可以使研究者在不同空间和时间尺度上对高分子聚合物的微观结构、相分离和动力学行为等进行详细的研究,进而阐明高分子微观结构与宏观性能的关联.该文以固体NMR中最主要的2类核(1 H和13 C)的检测技术为主线,简单介绍近年来固体NMR领域的一些最新研究进展及其在高分子结构和动力学研究中的应用.

With the advances in NMR theories and spectrometer hardware technology, NMR is playing an increasingly important role in studying multi-scale structure and dy-namics of polymers. In this paper, the newest developments in solid-state ^1H and 13^C NMR techniques and their applications in the studies of polymer structures and dynamics were reviewed. High-resolution solid-state ^1H NMR techniques, such as multiple-pulse and fast magic angle spinning （MAS）, have made it possible to determine the chemical structures of polymers and to detect the intra- and inter-polymer interactions effectively. Taking advantages of through-bond （J coupling） and through-space （dipolar coupling） interactions, two dimensional heteronuclear correlation NMR experiments now can be used to resolve the microstructures of complex polymer chains. The recoupling tech- niques allow dipolar interactions and chemical shift anisotropy to be observed under MAS conditions, thus enabling simultaneous detection of high-resolution ^1H or 13^C sig-nals and quasi-static anisotropic interactions. The domain sizes and interphase thickness in multiphase polymers and miscibility in polymer blends can now be determined effec-tively using the dipolar filter techniques. In the dynamics studies, it is now possible to obtain information on local fast motions of a single bond and super-slow chain dynamics by efficient suppression of spin-diffusion among protons and recoupling of chemical shift anisotropy. In summary, the advanced solid-state NMR techniques have enabled de-tailed studies on polymer microstructure, phase separation and dynamic behavior at dif- ferent time and length scales, and on the relationship between the microstructure and macroscopic properties of polymers.