Dielectric study: II. Structural transitions in the liquid crystalline phase of water-in-oil microemulsions
The complex permittivity, ϵ∗ = ϵ′ − jϵ″, of a water-in-dodecane microemulsion was studied in the frequency range 1.6 k Hz-50 MHz for water contents (mass fraction c) up to and beyond the inversion of the system into an oil-in-water type of dispersion. Within the concentration interval 0.31-0.41, lab...
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Published in | Journal of colloid and interface science Vol. 67; no. 3; pp. 457 - 464 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
Elsevier Inc
1978
|
Online Access | Get full text |
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Summary: | The complex permittivity, ϵ∗ = ϵ′ −
jϵ″, of a water-in-dodecane microemulsion was studied in the frequency range 1.6 k Hz-50 MHz for water contents (mass fraction
c) up to and beyond the inversion of the system into an oil-in-water type of dispersion. Within the concentration interval 0.31-0.41, labeled the nematic phase concentration region,
c
n
, the behavior of ϵ′ and ϵ″, upon concentration, exhibited an abrupt increase followed by a decreasing trend for
c >
C
n
. The phenomenon was observable only in the low-frequency range; after the first megahertz decade, it was no longer detectable. The frequency-dependent behavior of ϵ′ in the
c
n
region was comparable with that exhibited by the parallel component of the static dielectric constant (
ϵ
∥) of some oriented nematic liquid crystals with a positive dielectric anisotropy; the same analogy was found to apply to the frequency dependence of the microemulsion conductivity, σ(ν). Therefore, the peculiar dielectric behavior in the
c
n
region was ascribed to a structural transition, from a waterin-oil dispersion to a nematic liquid crystalline phase, which develops as the water content of the system approaches a given “transition concentration”
c
t
≈ 0.31. |
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ISSN: | 0021-9797 1095-7103 |
DOI: | 10.1016/0021-9797(78)90235-7 |