The 13C nuclear magnetic resonance spectra and spin-lattice relaxation times of crosslinked butyl rubbers

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.

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

MRS Proceedings ◽

10.1557/proc-339-675 ◽

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.

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

Applied Spectroscopy ◽

10.1366/0003702834634172 ◽

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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