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Shape fluctuations and water diffusion in microemulsion droplets : A nuclear spin relaxation study

Carlström, Göran LU orcid and Halle, Bertil LU (1989) In Journal of Physical Chemistry 93(8). p.3287-3299
Abstract

Water 2H and 17O spin relaxation data for the microemulsion phase in the AOT/D 2O/isooctane system are reported. The difference between the transverse (R 2) and the longitudinal (R 1) relaxation rates has been measured as function of droplet size, droplet volume fraction, temperature, and resonance frequency. The 2H longitudinal relaxation rate dispersion has been measured over an extensive frequency range, using the field-cycling technique. The focus in the study is on the contribution from slow molecular processes to the... (More)

Water 2H and 17O spin relaxation data for the microemulsion phase in the AOT/D 2O/isooctane system are reported. The difference between the transverse (R 2) and the longitudinal (R 1) relaxation rates has been measured as function of droplet size, droplet volume fraction, temperature, and resonance frequency. The 2H longitudinal relaxation rate dispersion has been measured over an extensive frequency range, using the field-cycling technique. The focus in the study is on the contribution from slow molecular processes to the quadrupolar relaxation behavior. For the first time in any system, the theoretically predicted relation between the 17O/ 2H ratios of quadrupolar line splittings and of R 2 - R 1 is verified. The extensive experimental data are used to discriminate among three different dynamic models. It is found that water diffusion within the microemulsion droplet cannot account for the experimental data. Instead, a substantial shape polydispersity seems to be required, where at any instant a large fraction of the droplets are nonspherical. However, it is not necessary that the equilibrium shape is nonspherical.

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publication status
published
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in
Journal of Physical Chemistry
volume
93
issue
8
pages
13 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:0001724768
ISSN
0022-3654
DOI
10.1021/j100345a080
language
English
LU publication?
yes
id
39a69e4f-c3dc-4e7a-b8c1-88314129d6bd
date added to LUP
2019-01-16 13:41:05
date last changed
2022-03-29 02:34:17
@article{39a69e4f-c3dc-4e7a-b8c1-88314129d6bd,
  abstract     = {{<p>Water                         <sup>2</sup>H and                         <sup>17</sup>O spin relaxation data for the microemulsion phase in the AOT/D                        <sub>2</sub>O/isooctane system are reported. The difference between the transverse (R                        <sub>2</sub>) and the longitudinal (R                        <sub>1</sub>) relaxation rates has been measured as function of droplet size, droplet volume fraction, temperature, and resonance frequency. The                         <sup>2</sup>H longitudinal relaxation rate dispersion has been measured over an extensive frequency range, using the field-cycling technique. The focus in the study is on the contribution from slow molecular processes to the quadrupolar relaxation behavior. For the first time in any system, the theoretically predicted relation between the                         <sup>17</sup>O/                        <sup>2</sup>H ratios of quadrupolar line splittings and of R                        <sub>2</sub> - R                        <sub>1</sub> is verified. The extensive experimental data are used to discriminate among three different dynamic models. It is found that water diffusion within the microemulsion droplet cannot account for the experimental data. Instead, a substantial shape polydispersity seems to be required, where at any instant a large fraction of the droplets are nonspherical. However, it is not necessary that the equilibrium shape is nonspherical.</p>}},
  author       = {{Carlström, Göran and Halle, Bertil}},
  issn         = {{0022-3654}},
  language     = {{eng}},
  month        = {{04}},
  number       = {{8}},
  pages        = {{3287--3299}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Journal of Physical Chemistry}},
  title        = {{Shape fluctuations and water diffusion in microemulsion droplets : A nuclear spin relaxation study}},
  url          = {{http://dx.doi.org/10.1021/j100345a080}},
  doi          = {{10.1021/j100345a080}},
  volume       = {{93}},
  year         = {{1989}},
}