NMR Spectra of polyimides: Interpretation and local chain motion study

Three kinds of high-performance polyimides 1 (poly(ketone-imide) PKI), 2 (poly(ether-imide) PEI) and 3 (poly(oxy-imide) POI) were studied using nuclear magnetic resonance (NMR). The NMR spectra of the polyimides were assigned according to the comprehensive consideration of the substitution effect of different substituting groups, viz. distortionless enhancement by polarization transfer (DEPT), no nuclear Overhauser effect (NNE), analysis of relaxation time, and two-dimensional correlated spectroscopy (COSY) techniques. The structural units of these three polyimides were determined. Carbon-13 and proton relaxation times for PEI and PKI were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (JS model) and anisotropic group rotation such as phenyl group rotation and methyl group rotation. Correlation times for the main-chain motion are in the tens of picosecond range which indicates the high flexibility of polyimide chains. Correlation times for phenyl group and methyl group rotations are more than 1 order of magnitude lower and approximately 1 order of magnitude higher than that of the main chain, respectively.

A NMR investigation on the interaction of lanthanide complexes with phospholipid bilayers

One and two dimentional NMR methods were used to investigate the interactions of lanthanide complexes (Lncit(2) and Ln-DTPA) with phospholipid bilayers, The results showed that in the phospholipid bilayers dispersion containing citrate ligand at pH 7.4, lanthanide ions would initially combine with citrate ligand and form Lncit, complexes which have little effect on the structure of phospholipid bilayers. Ln-DTPA complex does not affect the bilayers structure either. These results provided important experimental data for evaluating scientifically the toxicities of lanthanide ions when they were introduced into the biological body.

酞侧基聚芳醚酮的核磁共振研究（Ⅰ）──链结构及NMR谱的归属

用１Ｄ　ＮＭＲ方法研究酞侧基聚芳醚酮（ＰＥＫ－Ｃ）链结构，用二维同核化学位移相关与二维异核化学位移相关实验方法对１Ｄ　ＮＭＲ谱峰进行归属，探讨了二维异核远程相关实验在缩聚高分子研究中的应用，为ＰＥＫ－Ｃ修饰机理以及共混相容机理的研究提供重要信息。溶液ＮＭＲ谱图数据表明，ＰＥＫ－Ｃ具有较规整的链结构。

~(13)C NMR研究稀土柠檬酸配合物的溶液配位结构

用稀土离子诱导位移和顺磁弛豫时间测定等NMR方法研究了稀土柠檬酸配合物在pH7.4的溶液中的配位结构.结果表明稀土离子通过3-羟基和3-羧基与柠檬酸配体形成1:2的配合物,两个端羧基没有参与配位.通过计算稀土离子和柠檬酸配体中各个碳原子间的空间距离的相对比,建立了稀土离子与柠檬酸配体配位的新模式.

茂锆载体催化剂下的乙烯／辛烯共聚及聚合物的~（13）C NMR研究

茂锆载体催化剂下的乙烯／辛烯共聚及聚合物的~（１３）ＣＮＭＲ研究刘胜生，于广谦，黄葆同（中国科学院长春应用化学研究所长春１３００２２）关键词茂锆载体催化剂，共聚，序列分布，~（１３）ＣＮＭＲ由于茂锆催化剂具有高活性，单一活性中心等特点［１，２］，并且能...

H-1 and C-13 NMR studies of TTHA complexes with diamagnetic rare earth ions

TTHA complexes with diamagnetic rare earth ions (La3+, Y3+ and LU(3+)) were studied by H-1 and C-13 NMR spectroscopy. A symmetric structural model was suggested for La(TTHA) complex and an asymmetric model for Y(TTHA) and Lu(TTHA) complexes. The complex formation was dependent on the pH value of the solution. The interactions of La(TTHA) with the additional metal ions (La3+, Y3+ and Ca2+) were relatively weak, but relatively strong for that of Lu(TTHA) with the additional Lu3+.

A new topological index for the Changchun institute of applied chemistry C-13 NMR information system

A method to assign a single number representation for each atom (node) in a molecular graph, Atomic IDentification (AID) number, is proposed based on the counts of weighted paths terminated on that atom. Then, a new topological index, Molecular IDentification (MID) number is developed from AID. The MID is tested systematically, over half a million of structures are examined, and MID shows high discrimination for various structural isomers. Thus it can be used for documentation in the Changchun Institute of Chemistry C-13 NMR information system.

NMR-STUDY OF MISCIBILITY AND MORPHOLOGY OF POLYIMIDE POLYIMIDE BLENDS

The miscibility and morphology of polyimide/polyimide blends, PEI-E/PTI-E(a)) and PBPI-E/IPTI-E(a)), have been studied by means of C-13 CPMAS NMR technique. The results indicate that PEI-E/PTI-E blends are miscible on a molecular level, but molecular aggregation exists in pure PBPI-E specimen as well as PBPI-E/PTI-E blends with high content of PBPI-E, which vanishes in the blends with high content of PTI-E. When the content of PBPI-E is higher than that of PTI-E, the addition of PTI-E to PBPI-E has almost no effect on the size of the PBPI-E rigid domains, but has a large effect on the populations of the PBPI-E rigid domains. It is the intermolecular charge-transfer interaction that plays a critical role in the miscibility of PEI-E/PTI-E and PBPI-E/PTI-E blends.

STUDIES ON STRUCTURE OF EO/THF RANDOM COPOLYETHER(I) - NMR-STUDIES ON SOLUTION ACTION AND COMPLEX

The special action of TEO solution was investigated by 1D, 2D-NMR in CDCl3. For the present measurements, when the concentration of TEO was higher in CDCl3, the chemical shift difference (Delta delta) and the peak number of C-13 NMR spectrum were changed with increasing the solution concentration, At lower concentration(< 3% V/V ), the peaks will be closed together for -CH2O- resonance carbon and it is not the appearance of the narrowed, When temperature was changed, the Delta delta value was contrary to the solvent effect, So, the shifts of the resonance carbon in the NMR spectra indicated clearly that the complex formation for the system of CDCl3, and TEO molecular interaction were affected by the experiment temperature and the solution concentration.

A NMR-STUDY OF THE INTERACTION OF SILICA WITH DIPALMITOYLPHOSPHATIDYLCHOLINE LIPOSOMES

The interaction of silica with dipalmitoylphosphatidylcholine (DPPC) liposomes has been studied by detecting H-1 and 2D NOESY NMR spectra and measuring proton spin-lattice relaxation time (T-1). The antagonistic effect of aluminium citrate on silica has also been studied by measuring the proton T-1 values, The results show that silica particles mainly bind to the phosphate moiety of the polar headgroup of DPPC bilayers through hydrogen bonds between Si-OH and O-P groups, but they have no significant effect on the conformation of the choline group of the polar headgroup, The addition of silica particles decreases the mobilities of the hydrocarbon chains slightly, Proton T-1 data also indicate that aluminium citrate reduces the effect of silica, A possible mechanism for the toxicity of silica and the antagonistic effect of aluminium titrate on silica is suggested. (C) 1995 Academic Press Inc.

NMR-STUDY ON THE RELATIONSHIP BETWEEN MISCIBILITY AND ANTIAGING PERFORMANCE OF BLENDS CONTAINING BLOCK-COPOLYMERS

The anti-aging performance of blends of polystyrene (PS), styrene-butadiene triblock copolymers (SBS), and PS/styrene-butadiene (SB)-4A (Carm star SE block copolymer) has been studied by means of C-13 NMR techniques. It is found that the anti-aging performance of these kinds of blends largely depends on their miscibility with PS of different molecular weight M(PS). The larger the quantities of PS solubilized in polybutadiene (PBD) domains, the better the anti-aging performance of the blends. It is also found that the anti-aging performance of these blends has dependence on molecular architectures of the SE block copolymers. For the aged blends, the double bonds of PBD were broken, meanwhile serious cross-linking networks formed in the blends. The proposed anti-aging mechanism is that the PS solubilized in PBD domains can efficiently prevent oxygen molecules from diffusing into PBD domains, therefore, successfully stop the oxidative process of PBD.

H-1 NMR Titration Studies of Two Novel DTPA Derivatives

Polyaminopolycarboxylate gadolinium (III) complexes have been studied intensively in recent years because of their potential uses as contrast agents for magnetic resonance imaging (MHI)([1]). The research interests are mainly focussed on Gd3+ complexes of DTPA, DOTA and their various derivatives. Four kinds of Gd3+ complexes can be used presently in clinical MRI, which are GD(DTPA)([2]), Gd(DOTA)([3]), Gd(DTPA-BMA)([4]) and Gd(HP-DO3A)([5]). Here report two new DTPA bis (amide) derivatives-diethylenetriaminepentaacetic acid-N, N ''-bis (dimethylamide) (DTPA-BDMA) and -bis (diethylamide) (DTPA-BDEA).

EO／THF无规共聚醚结构研究（Ⅱ）──NMR方法研究溶剂配合物与溶液行为

用１Ｄ－ＮＭＲ和２Ｄ－ＮＭＲ方法研究了ＥＯ／ＴＨＦ共聚醚（ＴＥＯ）的溶液行为。ＴＥＯ在浓溶液状态，其溶液浓度不仅使谱峰化学位移值增减，而且使峰型发生较大的变化。当改变温度时，~（１３）ＣＮＭＲ谱在高场区有如同溶剂化效应的过程，实验结果表明：浓度与温度使ＴＥＯ溶液分子内部结构发生变化。２Ｄ－ＮＯＥＳＹ实验表明：在低浓度情况下，ＴＥＯ分子易与活泼氢溶剂生成配合物，分子间偶极－偶极相互作用受温度和浓度的影响。

稀土离子与红细胞作用的~(133)Cs NMR研究

随着稀土资源的不断开发利用,它们不可避免地通过多种途径进入生物体内,因而从分子和细胞水平上研究稀土的生物效应具有非常重要的理论和实际意义.关于稀土与细胞作用的研究已有诸多报道,本文报道用~(133)Cs NMR方法研究La~(3+)对Cs~+跨膜进入红细胞的影响.对于物质跨膜传输的研究,首先需要合适的手段将被传输物质在膜两侧的分布区分开.在碱金属离子中,仅~(133)Cs~+在不引入顺磁位移试剂情况下,细胞内外NMR信号能确切区分,并且在体系中无K~+时,Cs~+有类似于K~+的功能,故~(133)Cs是研究稀土离子与细胞作用