共查询到20条相似文献,搜索用时 109 毫秒
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基于核自旋探针的核磁共振(NMR)波谱技术可以在非常宽广的时间和空间尺度上提供重要的微观结构和动力学信息.固体NMR已成为阐明高分子中化学键变化、链间相互作用、多尺度结构与动力学演化,及其与宏观物理化学性质关系的有力工具.本文从基础原理、实验方法与技巧、典型应用与研究进展等几方面进行简要综述.在基础原理部分介绍了化学位... 相似文献
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固体核磁共振在高分子材料分析中的研究进展 总被引:3,自引:0,他引:3
简述固体核磁共振(NMR)技术的特点及其在高分子材料分析中的研究进展,着重介绍其在结构表征与反应进程监视、材料机械性能测定、动力学过程及多组分高分子材料研究中的主要方法。 相似文献
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高分子材料拥有众多优良的特性,使其广泛应用于现代社会的生产、生活及高新科技等领域。对于高分子特性的研究离不开微观物理、化学结构的定量表征。在众多表征高分子结构定量信息的实验技术中,固体核磁共振(SSNMR)发挥着重要的作用。它可以定量表征高分子的化学结构、材料体系的相成分及共混组分等,从而实现了难溶高分子产物的结构鉴定,以及高分子微观物理、化学结构关联材料性能的研究。然而,传统的SSNMR定量方法(直接激发法,DD)往往需要耗费十几个小时甚至数天的实验时间。交叉极化方法(CP)虽然大大缩短了实验时间,却往往无法提供定量的信息。基于此,研究者们提出了多个定量CP的实验方法,同时满足了方法定量性和实验耗时短的需求。本文综述了传统SSNMR定量方法及几种定量的CP方法,简单介绍了每个方法的基本原理,并平行阐述了实验方法的应用范围及特点,通过部分实例展示了SSNMR定量方法在高分子材料领域的应用价值,为研究者研发新型的高分子材料提供可靠并有效的结构表征手段。 相似文献
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高分子材料中的微观结构和动力学特征决定了材料的最终物理化学性能,并具有典型的时间和空间上的多尺度特性。在不同时空尺度上表征凝聚态下高分子中多尺度的结构、动力学及其动态演变等问题,进而阐明其结构-性能间的关系一直是高分子科学研究中的挑战性课题。目前,固体NMR技术已成为从原子至100nm的空间和10-9~10s的时间尺度上研究固态高聚物体系中多层次结构和复杂运动并阐明其结构与性能关系的有力工具。本文将综述我们近年来系统构建的多尺度固体NMR实验技术,及其在阐明高分子链结构、链间相容性和相互作用、界面相结构及相区尺寸、以及从高频到超慢链运动等问题中的应用。 相似文献
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运用固体核磁共振(NMR)技术研究了聚丙氨酸多肽片段(Ala)5与高分子齐聚物聚苯乙烯(PS, 分子量2000)及聚异戊二烯(PI, 分子量2210)共聚而成的类蜘蛛丝蛋白聚合物——聚苯乙烯-co-聚丙氨酸聚合物(PS-co-PAL)和聚异戊二烯-co-聚丙氨酸聚合物(PI-co-PAL)的结构及分子运动. 聚合物13C CP/MAS NMR(交叉极化/魔角旋转核磁共振)谱及其旋转坐标系中自旋-晶格弛豫时间(T1ρ(13C))的结果表明, 此两种聚合物中多肽片段(Ala)5具有相同的化学位移, 即相似的化学环境和二级结构, 并具有相近的T1ρ(13C), 即类似的聚集态结构. 聚合物的宏观力学性质明显不同: 常温下, PS-co-PAL呈硬颗粒状, PI-co-PAL呈橡胶状且易拉伸. 结果说明聚合物力学性质与高分子链段的性质密切相关. PI-co-PAL聚合物的PI链段, 其骨架—CH2CH—的T1ρ为(5.3±0.4) ms, 而PS-co-PAL聚合物的PS链段, 其骨架—CH2CH—的T1ρ为(47.0±5.5) ms, 说明二聚合物中PI链段较PS链段更为柔软. 另外, 基于密度泛函理论(DFT)的化学位移计算证明, 聚合物PS-co-PAL和PI-co-PAL中多肽片段(Ala)5的二面角均为(-131°, 142°), 说明它们以β-折叠构象存在. 相似文献
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Chao Jun JING Liu Sheng CHEN Yi SHI Xi Gao JIN 《中国化学快报》2005,16(11):1519-1522
^13C spin-lattice relaxation times (T1) of a conjugated polymer MEH-PPV in polymer/ layered silicate nanocomposites together with the steady state fluorescence emission and transient fluorescence decay measurements have been investigated. The T1 values of the conjugated carbons decrease dramatically according to the reduction of polymer concentration in the nano composites, while the fluorescence life times (τ) show a linear prolonging tendency. The results are explained from the point of view of molecular dynamics. 相似文献
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The phase behavior and motional mobility in binary blends of poly(4‐methylstyrene) (P4MS) and poly(cyclohexyl methacrylate) (PCHMA) have been examined by 13C solid state NMR techniques. The blend miscibility was studied by measuring the 1H spin‐relaxation times in the laboratory frame (T1H) and in the rotating frame (T1ρH), respectively. Although intermolecular spin diffusion contributes to the proton relaxations in accordance with homogeneity, T1ρH data shows signs of in complete averaging. The T1ρH relaxation behavior indicates the existence of heterogeneous do mains with shortest dimensions in the nanometer range, which is also sup ported by the intermolecular cross polarization experiments with variable contact times. In addition, according to the resuits of carbon T1ρ relaxation time measurements, it is concluded that mixing is intimate some what enough to cause a reduction in local chain mobility for P4MS and vice versa for PCHMA. 相似文献
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Ya Lin TANG* Xiao Zhong QU Liu Sheng CHEN Xi Gao JIN Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2001,(4)
A wide range of physical methods has been used for studying the sintering behavior of bulk polystyrene, which has been the subject of AFM imaging, DSC measurement, Dilatometer meadurement, Fourier IR, and solid state NMR studies to investigate the physicochemical change and its relation to the electronic and magnetic performance. In recent years, more attention was paid to the size effect on annealing temperature for the latex particles with the diameter of less than 100 nm, which present… 相似文献
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AnElectrochemicalStudyofPrusianBlueMicrocrystalinesMixedinPEO400PolymerElectrolytebySolid┐stateVoltammetryGUOLi-pingandLINXia... 相似文献
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用粗粒化的分子动力学(MD)模拟方法从分子层次研究了受限于粗糙壁内的聚合物熔体的动力学性质. 结果表明, 对于链长较短的受限聚合物熔体体系, 随着膜厚的增加, 体系内部高分子链的松弛时间逐渐减少; 然而对于链长较长的受限体系, 聚合物链的松弛时间随着膜厚的增加先减少后增加. 推测这种由于链长的变化所引起的动力学性质的差异源自受限熔体内聚合物链聚集状态的改变, 并且通过考察交叠参数对这种改变进行了分析. 结果表明, 在膜厚增加的过程中, 决定受限状态高分子长链松弛机理的因素逐渐从受限效应转变成为链间的缠结效应. 相似文献
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Amir Goldbourt Perunthiruthy K. Madhu 《Monatshefte für Chemie / Chemical Monthly》2002,133(12):1497-1534
Summary. Experimental and theoretical aspects of the multiple-quantum magic-angle spinning experiment (MQMAS) are discussed in this
review. The significance of this experiment, introduced by Frydman and Harwood, is in its ability to provide high-resolution NMR spectra of half-integer quadrupolar nuclei (I ≥ 3/2). This technique has proved to be useful in various systems ranging from inorganic materials to biological samples.
This review addresses the development of various pulse schemes aimed at improving the signal-to-noise ratio and anisotropic
lineshapes. Representative spectra are shown to underscore the importance and applications of the MQMAS experiment.
Corresponding author. E-mail: madhu@soton.ac.uk
Received April 16, 2002; accepted May 6, 2002 相似文献
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The feasibility of static deuterium rotating frame NMR relaxation measurements for characterization of slow timescale motions in powder systems is demonstrated. Using a model compound dimethyl sulfone-d6, we show that these measurements yield conformational exchange rates and activation energy values in accordance with results obtained with other techniques. Furthermore, we demonstrate that the full Liouvillian approach as opposed to the Redfield approximation is necessary to analyze the experimental data. 相似文献
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高分子固体电解质研究进展 总被引:6,自引:0,他引:6
高分子固体电解质具有质轻、粘弹性了、易成膜等许多无机电解质和有机溶剂电解质所不可比拟的优点,近年来得到了很大的发展,这种新型材料的应用主要集中开发全固态锂电池和锂离子电池。本文对SPE的电性能,离子传导特性以及提高SPE性能的途径等作了综述,并对其发展前景作了简要探讨。 相似文献
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Two inequivalent protons from 1H NMR spectra of RbH2AsO4 in the paraelectric phase were distinguished using static NMR and MAS NMR. From the 1H spin–lattice relaxation times in the laboratory frame, T1, and rotating frame, T1ρ, of the two crystallographically inequivalent hydrogen sites, i.e., H(1) and H(2), the temperature dependences of T1 and T1ρ for H(1) were related to the reorientational motion. The shorter H(1) bonds give rise to stronger H-bonds, and protons involved in stronger H-bonds have long relaxation times. Consequently, the RbH2AsO4 structure has two crystallographically inequivalent sites with two different hydrogen-bond lengths. 相似文献