Elucidation of Polymer Conformation, Phase Structure, and Dynamics by Multidimensional Solid-State NMR

9703916施密特-罗尔在这项研究计划中，发展了多维核磁共振技术，并应用于阐明固体聚合物中官能团的构象和运动，并将它们与宏观材料性能联系起来。所提出的用于表征无取向聚合物(如无定形聚合物和多肽)中链段构象的核磁共振技术是基于通过关联各向异性核磁共振耦合(偶极和化学位移各向异性)来测量相邻链段的相对取向。扭角信息是从所得到的2D或3D光谱中的特征强度图案中提取的。最终，在3D光谱中，2D化学位移关联模式将被偶极耦合分开。将对各种PET样品、聚苯乙烯和其他聚合物中的扭转角分布进行表征。双量子核磁共振技术已经被证明可以测量多肽中的扭转角，并将被应用于固体多肽材料。自旋扩散核磁共振将研究更大范围内的结构和迁移率，例如在相分离聚合物共混物中或在晶体-非晶界面上。在固体聚合物的分子动力学领域，由该PI部分引入的多维交换核磁共振方法阐明了聚合物中的松弛现象，这些松弛行为影响着许多宏观材料的性质。将开发新的交换核磁共振技术，例如，旨在检测小幅度或局部运动。运动过程，如螺旋跳跃，将被用来获得结构信息，例如表征聚合物链折叠。玻璃化转变上方聚合物中运动异质性的长度尺度将基于自旋扩散的空间信息来确定。%在这项研究计划中，用新的核磁共振技术在摩尔水平上研究了固体聚合物，如工程塑料和先进的生物材料。对分子结构和运动的洞察与机械性能(如韧性或蠕变)有关，最终将有助于工业改进聚合物材料的开发。来自三个系的学生将接受有关现代核磁共振理论和实践的指导，而几名研究生将接受在聚合物研究中使用最新的多维核磁共振技术的培训。***

9703916 Schmidt-Rohr In this research program, multidimensional nuclear magnetic resonance (NMR) techniques are developed and applied to elucidate the conformations and motions of functional groups in solid polymers and relate them to macroscopic materials properties. The proposed NMR techniques for characterizing segmental conformations in unoriented polymers, such as amorphous polymers and polypeptides, are based on measuring the relative orientations of adjacent segments by correlating anisotropic NMR couplings (dipolar and chemical-shift anisotropies). The torsion-angle informatiol is extracted from characteristic intensity patterns in the resulting 2D or 3D spectra. Eventually, in a 3D spectrum, 2D chemical-shift correlation patterns will be separated by dipolar couplings. The torsion-angle distributions in various PET samples, polystyrenes, and other polymers will be characterized. Double-quantum NMR techniques for measuring the torsion angles and in peptides have been demonstrated and will be applied to solid polypeptide materials. Structure and mobility on a larger scale, e.g. in phase-separating polymer blends or at the crystalline-amorphous interface, will be investigated by spin-diffusion NMR. In the area of molecular dynamics of solid polymers, multidimensional exchange NMR methods that were introduced in part by this PI have elucidated relaxations in polymers, which influence many macroscopic materials properties. New exchange NMR techniques will be developed, aiming, for instance, at detecting small-amplitude or localized motions. Motional processes, such as helical jumps, will be exploited for obtaining structural information, e.g. to characterize polymer chain folds. The length scale of motional heterogeneities in polymers above the glass transition will be determined based on spatial information from spin diffusion. %%%% In this research program, solid polymers such as engineering plastics and advanced biomaterials are investigated on a mole cular level by novel nuclear magnetic resonance (NMR) techniques. The insight into molecular structures and motions, which are related to mechanical properties such as toughness or creep, will ultimately help industry in the development of improved polymer materials. Students from three departments will be instructed about modern NMR in theory and practice, while several graduate students will be trained to use the latest multidimensional NMR techniques in polymer research. ***