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Title: Percolation in concentrated water-in-carbon dioxide microemulsions

Abstract

The phase behavior and electrical conductivity of water-in-carbon dioxide (W/C) microemulsions are reported over a range of temperatures (5--65 C), pressures (100--450 bar), and droplet volume fractions ({phi} = 0.0347-0.483) at a constant water-to-surfactant molar ratio (W{sub o}) of 12.5. A {phi} of 0.483 is a 5-fold increase over those reported previously. A critical point is observed at a droplet volume fraction of approximately 0.12, at which the single-phase microemulsion splits into two microemulsion phases of similar volume upon lowering the pressure (upper critical solution pressure). At low temperatures, a lower critical solution pressure is also observed upon increasing the pressure. Both of the critical solution pressures result from an increase in the attractive interdroplet interactions; consequently, pressure has little effect on the conductivity in the one-phase region. The conductivity increases nearly 3 orders of magnitude with changes in the droplet concentration or temperature. Scaling analysis of the conductivity data supports a dynamic percolation model, whereby the attractive interdroplet interactions form clusters of discrete droplets with rapid charge transport.

Authors:
; ;
Publication Date:
Research Org.:
Univ. of Texas, Austin, TX (US)
Sponsoring Org.:
National Science Foundation (NSF); USDOE
OSTI Identifier:
20075919
DOE Contract Number:  
FG03-96ER14664
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical
Additional Journal Information:
Journal Volume: 104; Journal Issue: 18; Other Information: PBD: 11 May 2000; Journal ID: ISSN 1089-5647
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; WATER; CARBON DIOXIDE; MICROEMULSIONS; ELECTRIC CONDUCTIVITY; DROPLETS; PHASE STUDIES; CHARGE TRANSPORT

Citation Formats

Lee, C.T. Jr., Bhargava, P., and Johnston, K.P. Percolation in concentrated water-in-carbon dioxide microemulsions. United States: N. p., 2000. Web. doi:10.1021/jp9941357.
Lee, C.T. Jr., Bhargava, P., & Johnston, K.P. Percolation in concentrated water-in-carbon dioxide microemulsions. United States. doi:10.1021/jp9941357.
Lee, C.T. Jr., Bhargava, P., and Johnston, K.P. Thu . "Percolation in concentrated water-in-carbon dioxide microemulsions". United States. doi:10.1021/jp9941357.
@article{osti_20075919,
title = {Percolation in concentrated water-in-carbon dioxide microemulsions},
author = {Lee, C.T. Jr. and Bhargava, P. and Johnston, K.P.},
abstractNote = {The phase behavior and electrical conductivity of water-in-carbon dioxide (W/C) microemulsions are reported over a range of temperatures (5--65 C), pressures (100--450 bar), and droplet volume fractions ({phi} = 0.0347-0.483) at a constant water-to-surfactant molar ratio (W{sub o}) of 12.5. A {phi} of 0.483 is a 5-fold increase over those reported previously. A critical point is observed at a droplet volume fraction of approximately 0.12, at which the single-phase microemulsion splits into two microemulsion phases of similar volume upon lowering the pressure (upper critical solution pressure). At low temperatures, a lower critical solution pressure is also observed upon increasing the pressure. Both of the critical solution pressures result from an increase in the attractive interdroplet interactions; consequently, pressure has little effect on the conductivity in the one-phase region. The conductivity increases nearly 3 orders of magnitude with changes in the droplet concentration or temperature. Scaling analysis of the conductivity data supports a dynamic percolation model, whereby the attractive interdroplet interactions form clusters of discrete droplets with rapid charge transport.},
doi = {10.1021/jp9941357},
journal = {Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical},
issn = {1089-5647},
number = 18,
volume = 104,
place = {United States},
year = {2000},
month = {5}
}