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

通过多维固态 NMR 阐明聚合物构象、相结构和动力学

• 批准号: 9703916
• 负责人: Klaus Schmidt-Rohr
• 金额: $ 24万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-05-01 至 2000-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9703916&HistoricalAwards=false
• 关键词: Elucidation; Polymer; Conformation; Phase; Structure

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. ***

小行星9703916 在这个研究项目中，多维核磁共振（NMR）技术被开发和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）中的链段构象的NMR技术是基于通过关联各向异性NMR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。扭转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化学位移相关模式将被偶极耦合分离。 将表征各种PET样品、聚苯乙烯和其他聚合物中的扭转角分布。 双量子核磁共振技术测量的扭转角和肽已被证明，并将应用于固体多肽材料。结构和流动性在更大范围内，例如在相分离的聚合物共混物或在结晶-无定形界面，将通过自旋扩散NMR进行研究。 在固体聚合物的分子动力学领域，本PI部分介绍的多维交换NMR方法已经阐明了聚合物中的弛豫，这影响了许多宏观材料的性质。将开发新的交换核磁共振技术，例如，旨在探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。基于自旋扩散的空间信息，将确定高于玻璃化转变的聚合物中运动不均匀性的长度尺度。 在这项研究计划中，固体聚合物，如工程塑料和先进的生物材料是在分子水平上通过新的核磁共振（NMR）技术进行研究。对分子结构和运动的深入了解，与韧性或蠕变等机械性能有关，最终将有助于工业开发改进的聚合物材料。来自三个系的学生将在理论和实践方面学习现代NMR，而几名研究生将接受培训，在聚合物研究中使用最新的多维NMR技术。 ***