Self-diffusion of polystyrene in solution 1. Experimental results of the NMR pulsed field gradient technique

1988 ◽  
Vol 266 (3) ◽  
pp. 201-207 ◽  
Author(s):  
G. Fleischer ◽  
O. E. Zgadzai ◽  
V. D. Skirda ◽  
A. I. Maklakov
Keyword(s):  
Field Gradient ◽  
Experimental Results ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Gradient Technique

On the limits of the application of the n.m.r. pulsed-field gradient technique for self-diffusion measurements in zeolites

Zeolites ◽  
1989 ◽  
Vol 9 (4) ◽  
pp. 299-302 ◽  
Author(s):  
Chr. Förste ◽  
W. Heink ◽  
J. Kärger ◽  
H. Pfeifer ◽  
N.N. Feokistova ◽  
...  
Keyword(s):  
Field Gradient ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Gradient Technique

Peculiarities of self-diffusion studies on polymer systems by the NMR pulsed field gradient technique

1985 ◽  
Vol 65 (3) ◽  
pp. 429-443 ◽  
Author(s):  
Gerald Fleischer ◽  
Dieter Geschke ◽  
Jösrg Karger ◽  
Wilfried Heink
Keyword(s):  
Field Gradient ◽  
Polymer Systems ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Diffusion Studies ◽  
Gradient Technique

NMR Pulsed Field Gradient Study of Self-Diffusion in the Isotropic Phase of the Liquid Crystals MBBA and EBBA

1979 ◽  
Vol 34 (8) ◽  
pp. 964-968 ◽  
Author(s):  
G. Rollmann ◽  
K. F. Reinhart ◽  
F. Noack
Keyword(s):  
Liquid Crystals ◽  
Field Gradient ◽  
Diffusion Coefficients ◽  
Isotropic Phase ◽  
Experimental Accuracy ◽  
Pulsed Field ◽  
Relaxation Analysis ◽  
Self Diffusion ◽  
Gradient Technique ◽  
First Time

AbstractIn refinement of a previous study made by Hayward and Packer, the self-diffusion coefficients D of the nematogen liquid crystals MBBA and EBBA were remeasured in the isotropic phase by means of the NMR pulsed field gradient technique. In particular, the diffusion measurements were made for the first time at different Larmor frequencies. A comparison with results obtained recently on the same samples by NMR T1 relaxation analysis reveals a severe discrepancy. Since the gradient method gives results in essential agreement with optical spectroscopies, the observed discrepancy must be attributed to shortages of the relaxation analysis (incorrect models, insufficient experimental accuracy). It is also shown that D depends more strongly on the molecular weight m than m-1/2 .

Measurement of the intracrystalline self-diffusion of xenon in zeolites by the NMR pulsed field gradient technique

1990 ◽  
Vol 112 (6) ◽  
pp. 2175-2178 ◽  
Author(s):  
Wilfried Heink ◽  
Joerg Kaerger ◽  
Harry Pfeifer ◽  
Frank Stallmach
Keyword(s):  
Field Gradient ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Gradient Technique

Pulsed Field Gradient NMR Investigation of Molecular Mobility of Trimethoxymethane in Nafion Membranes

1997 ◽  
Vol 496 ◽  
Author(s):  
Y. Wu ◽  
T. A. Za Wodzinski ◽  
M. C. Smart ◽  
S. G. Greenbaum ◽  
G.K.S. Prakash ◽  
...  
Keyword(s):  
Field Gradient ◽  
Molecular Mobility ◽  
Alternative Fuels ◽  
Direct Oxidation ◽  
Effective Distance ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Lower Extent ◽  
The Difference ◽  
Nmr Signals

ABSTRACTMolecular mobility of water and trimethoxymethane (TMM) in NAFION membranes of two different equivalent weights (EW), 1100 and 1500, were investigated. Self-diffusion coefficients were determined by the NMR pulsed field gradient method, using the water and methyl protons NMR signals, in saturated NAFION samples containing concentrations of TMM in water varying between 0.5 and 14 M, and at temperatures varying from 30°C to 80°C. Diffusion of molecular species containing methyl protons is more than a factor of two slower in the 1500 EW membrane than in the 1100 EW membrane at 30°C and 1 M concentration. The difference rises to about a factor of four at 80°C and 14 M concentration. These differences are attributed to the lower extent of plasticization of the higher EW material as well as the greater effective distance between acid functional groups. NAFION samples containing methanol/water mixtures were also investigated. Comparison with the methanol results and the permeation behavior, as characterized by gas Chromatographie methods, show that more than half of the TMM is hydrolyzed to methanol as it passes through the acidic membrane. The implications of these findings for alternative fuels in direct oxidation fuel cells are discussed.

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