Counterion spin relaxation in microemulsion droplets
(1992) In Journal of Physical Chemistry 96(23). p.9524-9531- Abstract
Counterion 23Na spin relaxation data are reported from the microemulsion phase in the AOT/water/isooctane system as a function of the water/AOT ratio, which determines the size of the aqueous droplets. The 23Na NMR measurements comprise three independent relaxation rates, allowing the individual spectral density values to be determined, as well as the second-order quadrupolar dynamic shift. The effect on the relaxation observables of counterion diffusion within the aqueous droplet core is calculated by solving the diffusion equation in the presence of the electrostatic mean field. This allows the 23Na NMR data to be interpreted in terms of the Na+ lateral diffusion coefficient Ds in... (More)
Counterion 23Na spin relaxation data are reported from the microemulsion phase in the AOT/water/isooctane system as a function of the water/AOT ratio, which determines the size of the aqueous droplets. The 23Na NMR measurements comprise three independent relaxation rates, allowing the individual spectral density values to be determined, as well as the second-order quadrupolar dynamic shift. The effect on the relaxation observables of counterion diffusion within the aqueous droplet core is calculated by solving the diffusion equation in the presence of the electrostatic mean field. This allows the 23Na NMR data to be interpreted in terms of the Na+ lateral diffusion coefficient Ds in the surface region, the residual quadrupole coupling constant χs, and a spectral density contribution Jf due to fast local motions. These quantities have also been determined in a previous 23Na NMR study of the reversed hexagonal phase of the same system, with similar results. Although the present data are basically consistent with the expected microstructure of closed droplets with highly mobile counterfoils, a model of monodisperse spherical droplets cannot account quantitatively for all the data. This discrepancy is tentatively ascribed to the existence of small reversed micelles coexisting with the classical microemulsion droplets.
(Less)
- author
- Kenéz, P. Huang ; Carlström, G. LU ; Furó, I. and Halle, B. LU
- organization
- publishing date
- 1992-01-01
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Journal of Physical Chemistry
- volume
- 96
- issue
- 23
- pages
- 8 pages
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- scopus:1542527694
- ISSN
- 0022-3654
- DOI
- 10.1021/j100202a082
- language
- English
- LU publication?
- yes
- id
- 02f3163f-a292-4aed-9154-ca274d13d4bd
- date added to LUP
- 2019-07-25 21:38:38
- date last changed
- 2022-03-29 02:34:20
@article{02f3163f-a292-4aed-9154-ca274d13d4bd, abstract = {{<p>Counterion <sup>23</sup>Na spin relaxation data are reported from the microemulsion phase in the AOT/water/isooctane system as a function of the water/AOT ratio, which determines the size of the aqueous droplets. The <sup>23</sup>Na NMR measurements comprise three independent relaxation rates, allowing the individual spectral density values to be determined, as well as the second-order quadrupolar dynamic shift. The effect on the relaxation observables of counterion diffusion within the aqueous droplet core is calculated by solving the diffusion equation in the presence of the electrostatic mean field. This allows the <sup>23</sup>Na NMR data to be interpreted in terms of the Na<sup>+</sup> lateral diffusion coefficient D<sub>s</sub> in the surface region, the residual quadrupole coupling constant χ<sub>s</sub>, and a spectral density contribution J<sub>f</sub> due to fast local motions. These quantities have also been determined in a previous <sup>23</sup>Na NMR study of the reversed hexagonal phase of the same system, with similar results. Although the present data are basically consistent with the expected microstructure of closed droplets with highly mobile counterfoils, a model of monodisperse spherical droplets cannot account quantitatively for all the data. This discrepancy is tentatively ascribed to the existence of small reversed micelles coexisting with the classical microemulsion droplets.</p>}}, author = {{Kenéz, P. Huang and Carlström, G. and Furó, I. and Halle, B.}}, issn = {{0022-3654}}, language = {{eng}}, month = {{01}}, number = {{23}}, pages = {{9524--9531}}, publisher = {{The American Chemical Society (ACS)}}, series = {{Journal of Physical Chemistry}}, title = {{Counterion spin relaxation in microemulsion droplets}}, url = {{http://dx.doi.org/10.1021/j100202a082}}, doi = {{10.1021/j100202a082}}, volume = {{96}}, year = {{1992}}, }