Application of fast field cycling proton NMR relaxation spectroscopy to a crystalline solid

Abstract Liquid crystalline compounds containing a cyano terminal group often exhibit peculiar molecular organizations of their mesophases. In this work we present proton NMR relaxation studies, performed by means of standard NMR and fast field-cycling NMR techniques, in the nematic (N) and bilayered smectic-A phase (SA2) of 4-pentyl-phenyl 4'-cyanobenzoyloxy-benzoate. The field-cycling measurements were used to clarify the relaxation behaviour in the low Larmor frequency range, where conventional techniques are not applicable. Self-diffusion and rotational reorientations are found to be the essential relaxation mechanisms at MHz frequencies in the smectic mesophase, while the contribution of collective modes appears only at lower frequencies in the kHz range. In the nematic mesophase the order director fluctuations mechanism dominates the relaxation dispersion up to 10 MHz, where the rotational reorientations become important, with minor corrections from the self-diffusion process. The agreement between the experimental findings and model fits could be improved by an additional relaxation mechanism in the kHz regime, ascribed to the interaction between protons and fast relaxing quadrupolar nitrogen 14N nuclei. Though all four processes are present in the nematic and smectic-A2 phases, the overall T1 frequency dependence is quite different in the two cases. This behaviour is discussed in terms of available theoretical calculations of the proton relaxation dispersion in liquid crystals, and it is also compared with data known from other cyano compounds.

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Investigation of Molecular Motion in Smectic Phases of the Liquid Crystal TBBA by NMR Relaxation Dispersion

Zeitschrift für Naturforschung A ◽

10.1515/zna-1980-0905 ◽

1980 ◽

Vol 35 (9) ◽

pp. 924-929 ◽

Cited By ~ 5

Author(s):

Th. Mugele ◽

V. Graf ◽

W. Wülfel

Keyword(s):

Nmr Relaxation ◽

Larmor Frequency ◽

Proton Spin ◽

Relaxation Dispersion ◽

Self Diffusion ◽

Smectic Phases ◽

Field Cycling ◽

The Difference ◽

Nmr Methods ◽

Fast Field

Abstract The proton spin T1 relaxation dispersion in the smectic A and C phase of TBBA, and for comparison also in the nematic phase, have been studied using time dependent fast field-cycling techniques in the Larmor frequency range from νp = 100 Hz to 44 MHz. Our measurements considerably extend recent ones by Blinc et al., performed with other NMR methods for frequencies ≧ 140 kHz. The new experimental data are consistent with the reported ones for Sm C but not for Sm A, the difference being that the essential T1 dispersion observed with our technique occurs at much lower frequencies, namely below about 100 kHz. As a consequence, the relaxation dispersion for both smectic phases looks very similar. It can be described quantitatively in terms of relaxation by "nematic-like" order fluctuations, self-diffusion, and by a third molecular mechanism with (for simplicity) Debve-like power spectrum, which is possibly a second type of order fluctuation or a molecular rotation about the short axis. The analysis reveals surprisingly far going parallels between the spin relaxation of simple smectics and that of high-temperature nematics like PAA.

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Dynamics and wettability of petroleum fluids in shale oil probed by 2D T 1 -T 2 and fast field cycling NMR relaxation

Microporous and Mesoporous Materials ◽

10.1016/j.micromeso.2017.05.055 ◽

2018 ◽

Vol 269 ◽

pp. 7-11 ◽

Cited By ~ 15

Author(s):

J.-P. Korb ◽

B. Nicot ◽

I. Jolivet

Keyword(s):

Nmr Relaxation ◽

Shale Oil ◽

Field Cycling ◽

Fast Field

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A compact X-Band resonator for DNP-enhanced Fast-Field-Cycling NMR

Journal of Magnetic Resonance ◽

10.1016/j.jmr.2016.08.002 ◽

2016 ◽

Vol 271 ◽

pp. 7-14 ◽

Cited By ~ 13

Author(s):

Oliver Neudert ◽

Carlos Mattea ◽

Siegfried Stapf

Keyword(s):

X Band ◽

Field Cycling ◽

Fast Field

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A proton NMR relaxation evaluation of a model of brain oedema fluid

Physics in Medicine and Biology ◽

10.1088/0031-9155/31/7/001 ◽

1986 ◽

Vol 31 (7) ◽

pp. 699-711 ◽

Cited By ~ 4

Author(s):

P S Allen ◽

M E Castro ◽

E O Treiber ◽

J A Lunt ◽

D P J Boisvert

Keyword(s):

Brain Oedema ◽

Proton Nmr ◽

Nmr Relaxation ◽

Oedema Fluid

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Insights into the translational and rotational dynamics of cations and anions in protic ionic liquids by means of NMR fast-field-cycling relaxometry

Physical Chemistry Chemical Physics ◽

10.1039/d0cp05440b ◽

2021 ◽

Vol 23 (4) ◽

pp. 2663-2675

Author(s):

Viviane Overbeck ◽

Henning Schröder ◽

Anne-Marie Bonsa ◽

Klaus Neymeyr ◽

Ralf Ludwig

Keyword(s):

Ionic Liquids ◽

Rotational Dynamics ◽

Protic Ionic Liquids ◽

Field Cycling ◽

Fast Field ◽

Hydrogen Bonded

NMR Fast-Field-Cycling (FFC) relaxometry provides important information about translational and rotational dynamics of hydrogen bonded protic ionic liquids (PILs).

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