Nuclear Magnetic Resonance Studies of Molecular Motion in Some Elastomers

1965 ◽  
Vol 38 (3) ◽  
pp. 517-525
Author(s):  
W. P. Slichter ◽  
D. D. Davis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Translational Motion ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Trans Content ◽  
Resonance Frequencies ◽  
Wide Range ◽  
Nuclear Magnetic

Abstract The nuclear magnetic resonance (NMR) relaxation has been studied in polyisobutylene and polybutadiene at temperatures from −175° to +200° C and at three resonance frequencies: 20, 30, and 50 Mc/sec. In polyisobutylene, the spin-lattice relaxation time (T1) passes through two minima with change in temperature. The low-temperature minimum is ascribed, as in other compounds, to methyl-group rotation, but in polyisobutylene this motion is found to encounter relatively large hindrance, presumably owing to interlocking among the groups. The high-temperature T1-minimum is ascribed to rotational and translational motion of the segments. The extent of motion is qualitatively gauged by calculation from the Bloembergen-Purcell-Pound theory for NMR relaxation in simple liquids. T1 is insensitive to molecular weight (M.W.) over a wide range, but the dependence of T2 upon M.W. changes abruptly when M.W.≅4×104. In polybutadiene, T1 is found to depend markedly on the cis-trans content.

Nuclear Magnetic Resonance Studies of δ-Stabilized Plutonium

2003 ◽  
Vol 802 ◽  
Author(s):  
N. J. Curro ◽  
L. Morales
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Frequency ◽  
Lattice Relaxation ◽  
Spin Fluctuations ◽  
Spin Lattice Relaxation ◽  
Cubic Symmetry ◽  
Magnetic Resonance Studies ◽  
Local Distortions ◽  
Nuclear Magnetic

Nuclear Magnetic Resonance studies of Ga stabilized δ-Pu reveal detailed information about the local distortions surrounding the Ga impurities as well as provides information about the local spin fluctuations experienced by the Ga nuclei. The Ga NMR spectrum is inhomogeneously broadened by a distribution of local electric field gradients (EFGs), which indicates that the Ga experiences local distortions from cubic symmetry. The Knight shift and spin lattice relaxation rate indicate that the Ga is dominantly coupled to the Fermi surface via core polarization, and is inconsistent with magnetic order or low frequency spin correlations.

Nuclear Magnetic Resonance Brain Imaging in Chronic Schizophrenia

1987 ◽  
Vol 150 (2) ◽  
pp. 161-163 ◽  
Author(s):  
J. A. O. Besson ◽  
F. M. Corrigan ◽  
G. R. Cherryman ◽  
F. W. Smith
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Lattice Relaxation ◽  
Chronic Schizophrenia ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Magnetic Resonance Brain Imaging ◽  
Normal Controls ◽  
Nuclear Magnetic

Patients with chronic schizophrenia were examined by nuclear magnetic resonance imaging of the brain. Subgroups of the syndrome with high positive or high negative symptom scores and ventricular dilatation were compared with each other and with normal controls in respect of regional spin lattice relaxation time (T1) changes. Significant differences were not observed between the schizophrenic subgroups and controls but there were significant differences between the subgroups themselves. The presence of tardive dyskinesia was associated with increased T1 of the basal ganglia. The significance of these results is discussed in relation to findings using other techniques.

Nuclear Magnetic Resonance Studies of Molecular Motion in Natural Rubber

1963 ◽  
Vol 36 (2) ◽  
pp. 318-324
Author(s):  
W. P. Slichter ◽  
D. D. Davis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Natural Rubber ◽  
Molecular Motion ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Spin Lattice ◽  
Nuclear Magnetic

Abstract Nuclear magnetic resonance measurements have been made on natural rubber to examine how frequency, temperature, and crystallinity affect the nuclear relaxation. Moecular motions were studied by observing NMR linewidths and spin-lattice relaxation times at temperatures between −100° and 100° C, and at radio frequencies between 2 and 60 Mc. The effect of crystallinity was seen in measurements on stark rubber. The relation between frequency and temperature in the spin-lattice relaxation process is examined in terms of the Arrhenius equation and the WLF expression. The importance of using frequency as a variable in NMR studies of molecular motion is stressed.

On the Structure of Thin diamond Films: A 1H and 13C Nuclear Magnetic Resonance Study

1994 ◽  
Vol 339 ◽  
Author(s):  
J. Shinar ◽  
M. Pruski ◽  
D. P. Lang ◽  
S.-J. Hwang ◽  
H. Jia
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spin Diffusion ◽  
Natural Diamond ◽  
Relaxation Times ◽  
Diamond Films ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

ABSTRACTThe 1H and 13C nuclear magnetic resonance (NMR) of thin diamond films deposited from naturally abundant (1.1 at.%) as well as 50% and 100% 13C-enriched CH4 heavily diluted in H2is described and discussed. Less than 0.6 at.% of hydrogen is found in the films which contain crystallites up to ∼15 μm across. The 1H NMR consists of a broad 50–65 kHz wide Gaussian line attributed to H atoms bonded to carbon and covering the crystallite surfaces. A narrow Lorentzian line was only occasionally observed and found not to be intrinsic to the diamonds. The 13C NMR demonstrates that >99.5% of the C atoms reside in a quaternary diamond-like configuration. The 13C spin-lattice relaxation times T1 are four orders of magnitude shorter than in natural diamond and believed to be due to 13C spin diffusion to paramagnetic centers, presumably carbon dangling bonds. Analysis of T1 indicates that within the 13C spin diffusion length of ∼0.05 μm these centers are uniformly distributed in the diamond crystallites, possibly concentrated on the internal surfaces of a relatively dense system of nanovoids.

Solute 13C Nuclear Magnetic Resonance Spectrometric Investigation of Acetonitrile-Tetraalkylammonium Salt Interactions

1983 ◽  
Vol 37 (1) ◽  
pp. 29-31
Author(s):  
Neal R. Dando ◽  
Harvey S. Gold ◽  
Cecil Dybowski
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Salt Concentration ◽  
Alkyl Chain ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

Carbon-13 nuclear magnetic resonance spectrometry is used to observe changes in the spin-lattice relaxation time ( T1) of the alkyl chain carbons of symmetric tetraalkylammonium salts ( R4N+) X− in acetonitrile as a function of salt concentration in the range from 0.25 to 1.4 M. The T1 values of the alkyl chain carbons are observed to be differentially sensitive to salt concentration, the sensitivity being greatest at the α carbon position. These observations suggest accessibility of the cation nitrogen to solvent molecules and changing microviscosity about the salt molecule.

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