Molecular Dynamics of Monomer, Oligomer, and Polymer Liquids in Porous Media: A Field-Cycling Nmr Relaxometry and NMR Field-Gradient Diffusometry Study

1994 ◽  
Vol 366 ◽  
Author(s):  
R. Kimmich ◽  
S. Stapf ◽  
R.-O. Seitter ◽  
P. Callaghan ◽  
E. Khozina
Keyword(s):  
Molecular Dynamics ◽  
Porous Media ◽  
Field Gradient ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Porous Matrix ◽  
Spin Lattice Relaxation ◽  
Nmr Relaxometry ◽  
Lévy Walks ◽  
Field Cycling

ABSTRACTThe molecular dynamics of fluids in porous media has been studied using field-cycling NMR relaxometry and NMR field-gradient diffusometry. The frequency dependences of the 1H and 2H spin-lattice relaxation times T1 of various liquids in porous glass reveal weak and strong adsorption behaviour depending on the polarity of the adsorbates. Correlation times eight orders of magnitude longer than in bulk have been observed. The T1 dispersion moreover reflects geometrical details of the matrix in a length scale three orders of magnitude longer than the adsorbate molecules. The mean-square displacements of adsorbate molecules on the surface are only one order of magnitude less than in bulk. The global diffusivity is reduced by tortuosity and porosity effects. The observed phenomena may be explained by bulk-mediated surface diffusion, i.e., Lévy walks. The dynamics of polymer chains much longer than the pore size is characteristicly different from that in bulk melts. There is evidence that the reptation mechanism explains at least a part of the phenomena observed for the porous matrix in contrast to findings with bulk polymer melts.

Time Domain Zero Field NMR and NQR

1986 ◽  
Vol 41 (1-2) ◽  
pp. 440-444 ◽  
Author(s):  
A. Bielecki ◽  
D. B. Zax ◽  
A. M. Thayer ◽  
J. M. Millar ◽  
A. Pines
Keyword(s):  
Time Domain ◽  
Relaxation Times ◽  
Low Frequency ◽  
High Sensitivity ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Zero Field ◽  
Spin Lattice ◽  
Field Cycling ◽  
The Time Domain

Field cycling methods are described for the time domain measurement of nuclear quadrupolar and dipolar spectra in zero applied field. Since these techniques do not involve irradiation in zero field, they offer significant advantages in terms of resolution, sensitivity at low frequency, and the accessible range of spin lattice relaxation times. Sample data are shown which illustrate the high sensitivity and resolution attainable. Comparison is made to other field cycling methods, and an outline of basic instrumental requirements is given.

scholarly journals NMR relaxometry: Spin lattice relaxation times in the laboratory frame versus spin lattice relaxation times in the rotating frame

2010 ◽  
Vol 495 (4-6) ◽  
pp. 287-291 ◽  
Author(s):  
Emilie Steiner ◽  
Mehdi Yemloul ◽  
Laouès Guendouz ◽  
Sébastien Leclerc ◽  
Anthony Robert ◽  
...  
Keyword(s):  
Relaxation Times ◽  
Lattice Relaxation ◽  
Laboratory Frame ◽  
Spin Lattice Relaxation ◽  
Rotating Frame ◽  
Spin Lattice ◽  
Nmr Relaxometry

2 D Methods in NQR Spectroscopy

1992 ◽  
Vol 47 (1-2) ◽  
pp. 333-341
Author(s):  
J. Seliger ◽  
R. Blinc
Keyword(s):  
Double Resonance ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Electric Quadrupole ◽  
Quadrupole Coupling Constant ◽  
Spin Lattice Relaxation ◽  
Two Dimensional ◽  
Spin Lattice ◽  
Quadrupole Coupling ◽  
Field Cycling

AbstractThe application of two-dimensional spectroscopy to nuclear quadrupole resonance (NQR) is reviewed with special emphasys on spin 3/2 nuclei. A new two-dimensional level crossing double resonance NQR nutation technique based on magnetic field cycling is described. This technique allows for a determination of both the electric quadrupole coupling constant and the asymmetry parameter for spin 3/2 nuclei in powdered samples even in cases where the quadrupolar signals are too weak to be observed directly. It works if the usual double resonance conditions are met, i.e. if the spin-lattice relaxation times are not too short if the quadrupolar nuclei are dipolarly coupled to "strong" nuclei. Variations of this techique can be also used for 2 D "exchange" NQR spectroscopy and NQR imaging.

Formation of p-cresol:piperazine complex in solution monitored by spin–lattice relaxation times and pulsed field gradient NMR diffusion measurements

2003 ◽  
Vol 164 (2) ◽  
pp. 197-204 ◽  
Author(s):  
Erika Martins de Carvalho ◽  
Marcia Helena Rodrigues Velloso ◽  
Luzineide Wanderley Tinoco ◽  
José Daniel Figueroa-Villar
Keyword(s):  
Field Gradient ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field ◽  
Spin Lattice ◽  
Nmr Diffusion

Molecular Dynamics in the Solid Trimethylamine-Borane Complex: A Deuterium NMR Study

1995 ◽  
Vol 50 (1) ◽  
pp. 81-89 ◽  
Author(s):  
Glenn H. Penner ◽  
Baiyi Zhao ◽  
Kenneth R. Jeffrey
Keyword(s):  
Molecular Dynamics ◽  
Variable Temperature ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Activation Energies ◽  
Spin Lattice Relaxation ◽  
Deuterium Nmr ◽  
Molecular Orbital Calculations ◽  
Spin Lattice ◽  
Nmr Study

Abstract The molecular dynamics of solid (CH3)3NBH3 is investigated by deuterium NMR spectroscopy. Variable temperature lineshape analyses yield activation energies of 27 ± 3, 19 ± 2, and 12.5 ± 2 kJ/mol for -CH3, -N(CH3)3 and -BH3 rotation, respectively. Analysis of the temperature depen­ dence of the spin-lattice relaxation times, T1 , gives activation energies of 33 ± 3, 15 ± 1.5, and 14 ± 1.5 kJ/mol, respectively. Direct comparison of rotational exchange rates (from lineshape simu­ lations) an of rotational correlation times (from T1 analyses) for -N(CH3)3 and -BH3 rotation indicate that the two motions are correlated in solid (CH3)3NBH3 and together constitute a whole molecule reorientation about the N-B bond. This is supported by an internal rotational barrier of 18.0 kJ/mol for-BH3 rotation, obtained from ab initio molecular orbital calculations at the MP2/6-31G* level.

scholarly journals Effect of methylene chain length of perovskite-type layered [NH3(CH2)nNH3]ZnCl4 (n = 2, 3, and 4) crystals on thermodynamic properties, structural geometry, and molecular dynamics

RSC Advances ◽  
2021 ◽  
Vol 11 (60) ◽  
pp. 37824-37829
Author(s):  
Ae Ran Lim
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Inverse Temperature ◽  
Structural Geometry ◽  
Spin Lattice ◽  
H Nmr ◽  
Perovskite Type

1H NMR spin–lattice relaxation times T1ρ of [NH3(CH2)nNH3]ZnCl4 (n = 2, 3, and 4) as a function of inverse temperature. The solid lines represent activation energy.

Multinuclear Quadrupole Resonance Studies of Biological Systems

1990 ◽  
Vol 45 (3-4) ◽  
pp. 273-292 ◽  
Author(s):  
Yukio Hiyama
Keyword(s):  
Quadrupole Interaction ◽  
Biological Systems ◽  
Relaxation Times ◽  
Substituent Effects ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Quadrupole Resonance ◽  
Field Cycling

Abstract We have employed multinuclear quadrupole resonance, using the field cycling technique, to study the structure of heterocyclic biomolecules. The electron density at nitrogen was investigated by the Townes-Dailey model of 14N NQR. Large substituent effects were evident especially on the n orbitals. Electron transfer through H-bonds also affects the 14 N quadrupole interaction. Deuterium quadrupole resonance at exchangeable sites was also utilized. Since the deuterium quadrupole correlation coefficient is sensitive to the geometry of H-bonds, the intermolecular distance of the pyrrole-pyridine complex could be determined. The field cycling technique is sensitive enough to detect 14 N ··· 14 N double transitions in parabanic acid thanks to the long spin-lattice relaxation time. However in many biological systems, such as hydrates, the technique is hardly applicable because of the short proton relaxation times. In such cases the solid state NMR technique was utilized. The 2H NMR spectrum of thymidine reveals interesting static and dynamical features of deuterium quadrupole interaction.

A deuterium NMR study of guest molecular dynamics of acetone in two organic inclusion compounds

1995 ◽  
Vol 73 (12) ◽  
pp. 2196-2207 ◽  
Author(s):  
Paul S. Sidhu ◽  
Jason Bell ◽  
Glenn H. Penner ◽  
Kenneth R. Jeffrey
Keyword(s):  
Molecular Dynamics ◽  
Inclusion Compounds ◽  
Nmr Spectra ◽  
Guest Molecule ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Deuterium Nmr ◽  
Spin Lattice ◽  
Nmr Study

Deuterium nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation times (T1) are used to investigate the dynamics of the guest molecule, acetone, in tris(5-acetyl-3-thienyl)methane (TATM) and cyclotriveratrylene (CTV) inclusion compounds. 13C CPMAS powder NMR spectra were obtained for each clathrate, to verify inclusion. In acetone: TATM, the guest molecule is undergoing twofold reorientation about the CO bond, exchanging the two methyl groups. An activation energy of 20 (± 1.4) kJ/mol, for the two-site jump motion, was found, independently, from deuterium NMR spectra an T1 measurements. Acetone in CTV performs the same type of motion as acetone in TATM. Activation energies of 25.0 (± 3.2) kJ/mol and 24.1 (± 0.5) kJ/mol were determined using the same two techniques. both inclusion compounds, the rate of methyl rotation within the acetone molecule is greater than 108 Hz even at the lowest temperature measured (84 K). Analytical expressions for the spin-lattice relaxation time (T1), for a twofold jump, were derived. Calculated values of the effective quadrupolar coupling constant and T1min for the guests agree very well with the experimental data. The 84 K spectrum of acetone:TATM unexpectedly shows some asymmetry, the origin of which is discussed. Finally, these two clathrates are compared to the recently examined acetone: tri-ortho-thymotide inclusion compound. Key words: inclusion compounds, deuterium NMR, solid state NMR spectroscopy, molecular dynamics.

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