US EPA

3860151 

Journal Article 

PULSED GRADIENT NMR-STUDY OF ANISOTROPIC SURFACTANT DIFFUSION IN THE CESIUM PERFLUORO OCTANOATE/D2O SYSTEM 

Ukleja, P; Chidichimo, G; Photinos, P 

1991 

1 

Liquid Crystals
ISSN: 0267-8292 

TAYLOR & FRANCIS LTD 

LONDON 

9 

3 

359-367 

10.1080/02678299108045570 

WOS:A1991FB68500004 

We use pulsed field gradient F-19 NMR to measure the diffusion coefficients of surfactant molecules in the isotropic and lamellar phases of the caesium perfluoro octanoate (CsPFO)/D2O system. An aligned lamellar sample is created by cooling through the nematic phase in the presence of a 1.4 T magnetic field. The director in the lamellar phase does not respond to ordinary field strengths, thus the aligned sample can be rotated clockwise or counterclockwise to place the director at a magic angle, where measurement of diffusion coefficients becomes possible. From a pair of so-obtained coefficients, we derive the principal values of the diffusion tensor corresponding to the directions parallel and perpendicular to the director (D-parallel-to and D-perpendicular-to). We found D-perpendicular-to to be at least 20 times D-parallel-to, a much larger anisotropy than is seen in electrical conductivity and water diffusion in similar systems. These results are compared to electrical conductivity, water and dye diffusion measurements.