ALGORITHM FOR VERIFICATION OF THE WLF THEORY FOR THE DIFFUSION OF SMALL MOLECULES IN SOME POLYMERIC SOLUTIONS

2005 ◽  
Vol 19 (27) ◽  
pp. 4125-4133 ◽  
Author(s):  
M. TODICA
Keyword(s):  
Magnetic Field ◽  
Small Molecules ◽  
Pulse Magnetic Field ◽  
Magnetic Field Gradient ◽  
Preliminary Investigation ◽  
The Self ◽  
Free Volume Theory ◽  
Self Diffusion ◽  
Polymeric Solutions ◽  
Self Diffusion Coefficient

The self-diffusion coefficient of the cyclohexane in some polybutadiene solutions was measured by NMR pulse magnetic field gradient method. The experimental data were analyzed on the basis of the free volume theory. A specific algorithm for analyze was proposed. Preliminary investigation indicates a deviation from the WLF theory for these solutions.

ALGORITHM FOR THE EVALUATION OF THE SELF-DIFFUSION COEFFICIENT OF SMALL MOLECULES, USING THE NMR MAGNETIC FIELD GRADIENT METHOD

2002 ◽  
Vol 16 (19) ◽  
pp. 2875-2884 ◽  
Author(s):  
M. TODICA ◽  
A. V. POP
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficient ◽  
Small Molecules ◽  
Field Gradient ◽  
Spin Echo ◽  
Magnetic Field Gradient ◽  
Pure Water ◽  
The Self ◽  
Self Diffusion ◽  
Self Diffusion Coefficient

Different methods of investigation of the spin-echo attenuation, in the NMR pulsed field gradient experiments, were analyzed in order to optimize the measurements of the self-diffusion coefficient of the small molecules of simplest liquids. A particular algorithm of representation of the experimental data is proposed in order to eliminate the effect of the residual gradient. This algorithm, tested for pure water, give results in accord with the literature.

Temperature and Pressure Dependence of Self Diffusion in Octamethylcyclotetrasiloxane and Hexamethylcyclotrisilazane

1990 ◽  
Vol 45 (11-12) ◽  
pp. 1281-1284 ◽  
Author(s):  
A. Greiner-Schmid ◽  
M. Has ◽  
H.-D. Lüdemann
Keyword(s):  
Magnetic Field ◽  
Pressure Dependence ◽  
Spin Echo ◽  
The Self ◽  
Self Diffusion ◽  
Field Gradients ◽  
Magnetic Field Gradients ◽  
Temperature And Pressure ◽  
Spin Echo Technique ◽  
Self Diffusion Coefficient

AbstractThe pressure dependence of the self diffusion coefficient D for octamethylcyclotetrasiloxane and hexamethylcyclotrisilazane has been determined by the NMR spin echo technique with pulsed magnetic field gradients at pressures up to 200 MPa and at temperatures between 490 K and 290 K. The data extend partially into the deeply supercooled range. The isobaric temperature dependence of these data is quantitatively described by the empirical Vogel-Fulcher-Tammann equation. For both substances the melting pressure curves were determined in addition.

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