Line Narrowing in Solid-State Proton NMR with Acquisition Delay

Fung, B. M.; Tong, T.‐H.; Dollase, Thilo; Magnuson, Matthew L.

doi:10.1006/jmra.1996.0213

Cited by 13 publications

(11 citation statements)

References 4 publications

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“…For many organic solids without MAS, a few narrow peaks can often be detected with an acquisition delay of about 100 ls, but their intensities quickly diminish with longer delay times [11][12][13][14]. This is the case for adamantane, hexamethylbenzene, and to a lesser extent, poly(vinyl stearate) (Figs.…”

Section: Resultsmentioning

confidence: 95%

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The presence of long-lived spin states in organic solids with rapid molecular motions

Fung

Ermakov

2004

Journal of Magnetic Resonance

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Section: Resultsmentioning

confidence: 95%

“…Interpretations on the origin of these peaks are controversial [11][12][13][14]. Nevertheless, we have found that this phenomenon is much more pronounced for organic solids with rapid molecular motions.…”

Section: Introductionmentioning

confidence: 88%

The presence of long-lived spin states in organic solids with rapid molecular motions

Fung

Ermakov

2004

Journal of Magnetic Resonance

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“…The memory effect seems to play an important role in spin relaxation, and it has been suggested that the acquisition delay filters out the immobile components within the solid, allowing the remaining small fraction of species undergoing isotropic motion to be detected . It has also been proposed that the broad signal acquired without delay is composed of numerous overlapping peaks representing a range of transition frequencies and SPEDA simply removes most of these peaks . Thus, it is uncertain whether SPEDA yields true isotropic shifts, and since SPEDA does not eliminate spinning sidebands, this further complicates spectral interpretation.…”

Section: Resultsmentioning

confidence: 99%

Structural Correlation Study of Pulsed Plasma-Polymerized Fluorocarbon Solids by Two-Dimensional Wide-Line Separation NMR Spectroscopy

Lau

Gleason

1997

J. Phys. Chem. B

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Two-dimensional wide-line separation (WISE) NMR spectroscopy has been applied to obtain structural correlation in fluorocarbon films deposited via a pulsed plasma enhanced chemical vapor deposition. Films from two pulsed deposition conditions, 10/20 and 10/400 ms on/off times, were analyzed in detail. Onedimensional 19 F and 13 C NMR results agreed well with prior studies of these films using X-ray photoelectron spectroscopy, which showed greater CF 2 fractions with decreasing pulsed deposition duty cycle. 13 C CPMAS studies, in addition, distinguished between unsaturated and saturated fluorocarbon species in these films. However, 19 F-13 C WISE allowed further differentiation of fluorocarbon moieties by the difference in nearestneighbor connectivity. The 10/20 film showed a prevalence of at least two inequivalent CF 3 species. A weak presence of unsaturated )CF-species was also detected. No specific CF 2 moiety was resolved, which was attributed to significant chemical shift dispersion and heterogeneity in CF 2 bonding environment. In contrast, the 10/400 film displayed an increased proportion of CF 2 species, predominantly as -CF 2 CF 2 -and CF 3 CF 2 -groups, and less CF 3 termination, indicative of a structure approaching that of poly(tetrafluoroethylene). These observations support the hypothesis of a less aggressive deposition environment, inducing less cross-links and unsaturation and promoting linear chain propagation, with a longer pulse off-time during deposition. Spinning sideband patterns in the 19 F dimension of NMR spectra did not severely hinder spectral interpretation but instead offered a means of revealing motional differences in the fluorocarbon moieties.

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“…Gerstein et al have shown [52] that significantly delayed acquisition proton spectra can reveal the existence of mobile moieties in a solid system even at a very low concentration, though the cause of this effect is subject to controversy. [53,54] DP methods are, naturally, available for perfluorinated systems also. For fluoropolymers containing protons, direct detection of their 1 H spectra is also possible (as well as 19 F !…”

Section: Relaxation In Homogeneous and Heterogeneous Samplesmentioning

confidence: 99%

“…The effects depend on offset and shielding anisotropy (both of which are much larger for F than the corresponding parameters for proton NMR) but not significantly on dipolar interactions. Gerstein et al have shown52 that significantly delayed acquisition proton spectra can reveal the existence of mobile moieties in a solid system even at a very low concentration, though the cause of this effect is subject to controversy 53,54. DP methods are, naturally, available for perfluorinated systems also.…”

Section: Discriminating Experiments In 19f Solid‐state Nmr Spectroscopymentioning

confidence: 99%

Selective NMR Pulse Sequences for the Study of Solid Hydrogen‐Containing Fluoropolymers

Ando

Harris

Hazendonk

et al. 2005

Macromol. Rapid Commun.

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Summary: Fluorine‐19 NMR spectra of solids have some special features, which are discussed in this article. In particular, they generally contain two abundant spin baths (protons and fluorine nuclei). This situation throws up some special operational requirements, as does the study of heterogeneous samples. The relaxation characteristics of heterogeneous systems, which are briefly described herein, frequently permit the use of specific pulse sequences to obtain subspectra for individual components. Various possible selective sequences for use in fluorinated heterogeneous organic solids are listed and their actions rationalized on the basis of molecular mobility. Semicrystalline hydrogen‐containing fluoropolymers form especially suitable systems for such operations, and in order to understand their domain structures it is essential to obtain subspectra of the amorphous and crystalline domains. Examples are given of the use of selective pulse sequences for studying fluoropolymers, especially for poly(vinylidene fluoride) (PVDF) and the copolymer P(VDF75/TrFE25) (TrFE = trifluoroethylene).

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Line Narrowing in Solid-State Proton NMR with Acquisition Delay

Cited by 13 publications

References 4 publications

The presence of long-lived spin states in organic solids with rapid molecular motions

The presence of long-lived spin states in organic solids with rapid molecular motions

Structural Correlation Study of Pulsed Plasma-Polymerized Fluorocarbon Solids by Two-Dimensional Wide-Line Separation NMR Spectroscopy

Selective NMR Pulse Sequences for the Study of Solid Hydrogen‐Containing Fluoropolymers

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