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Title: Lamellar Gels and Spontaneous Vesicles in Catanionic Surfactant Mixtures

Abstract

Caill{acute e} analysis of the small-angle X-ray line shape of the lamellar phase of 7:3 wt/wt cetyltrimethylammonium tosylate (CTAT)/sodium dodecylbenzene sulfonate (SDBS) bilayers shows that the bending elastic constant is {kappa}= (0.62 {+-} 0.09)kBT. From this and previous results, the Gaussian curvature constant is {kappa}= (-0.9 {+-} 0.2)kBT. For 13:7 wt/wt CTAT/SDBS bilayers, the measured bending elasticity decreases with increasing water dilution, in good agreement with predictions based on renormalization theory, giving {kappa}{sub 0} = 0.28k{sub B}T. These results show that surfactant mixing is sufficient to make {kappa} {approx} k{sub B}T, which promotes strong, Helfrich-type repulsion between bilayers that can dominate the van der Waals attraction. These are necessary conditions for spontaneous vesicles to be equilibrium structures. The measurements of the bending elasticity are confirmed by the transition of the lamellar phase of CTAT/SDBS from a turbid, viscoelastic gel to a translucent fluid as the water fraction is decreased below 40 wt %. Freeze-fracture electron microscopy shows that the gel is characterized by spherulite defects made possible by spontaneous bilayer curvature and low bending elasticity. This lamellar gel phase is common to a number of catanionic surfactant mixtures, suggesting that low bending elasticity and spontaneous curvature are typical of thesemore » mixtures that form spontaneous vesicles.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914106
Report Number(s):
BNL-78674-2007-JA
Journal ID: ISSN 0743-7463; LANGD5; TRN: US200804%%312
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Langmuir; Journal Volume: 22
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AMMONIUM COMPOUNDS; SODIUM COMPOUNDS; SULFONATES; SURFACTANTS; MIXTURES; ELASTICITY; MORPHOLOGY; GELS; national synchrotron light source

Citation Formats

Coldren,B., Warriner, H., van Zanten, R., and Zasadzinski, J.. Lamellar Gels and Spontaneous Vesicles in Catanionic Surfactant Mixtures. United States: N. p., 2006. Web. doi:10.1021/la052447x.
Coldren,B., Warriner, H., van Zanten, R., & Zasadzinski, J.. Lamellar Gels and Spontaneous Vesicles in Catanionic Surfactant Mixtures. United States. doi:10.1021/la052447x.
Coldren,B., Warriner, H., van Zanten, R., and Zasadzinski, J.. Sun . "Lamellar Gels and Spontaneous Vesicles in Catanionic Surfactant Mixtures". United States. doi:10.1021/la052447x.
@article{osti_914106,
title = {Lamellar Gels and Spontaneous Vesicles in Catanionic Surfactant Mixtures},
author = {Coldren,B. and Warriner, H. and van Zanten, R. and Zasadzinski, J.},
abstractNote = {Caill{acute e} analysis of the small-angle X-ray line shape of the lamellar phase of 7:3 wt/wt cetyltrimethylammonium tosylate (CTAT)/sodium dodecylbenzene sulfonate (SDBS) bilayers shows that the bending elastic constant is {kappa}= (0.62 {+-} 0.09)kBT. From this and previous results, the Gaussian curvature constant is {kappa}= (-0.9 {+-} 0.2)kBT. For 13:7 wt/wt CTAT/SDBS bilayers, the measured bending elasticity decreases with increasing water dilution, in good agreement with predictions based on renormalization theory, giving {kappa}{sub 0} = 0.28k{sub B}T. These results show that surfactant mixing is sufficient to make {kappa} {approx} k{sub B}T, which promotes strong, Helfrich-type repulsion between bilayers that can dominate the van der Waals attraction. These are necessary conditions for spontaneous vesicles to be equilibrium structures. The measurements of the bending elasticity are confirmed by the transition of the lamellar phase of CTAT/SDBS from a turbid, viscoelastic gel to a translucent fluid as the water fraction is decreased below 40 wt %. Freeze-fracture electron microscopy shows that the gel is characterized by spherulite defects made possible by spontaneous bilayer curvature and low bending elasticity. This lamellar gel phase is common to a number of catanionic surfactant mixtures, suggesting that low bending elasticity and spontaneous curvature are typical of these mixtures that form spontaneous vesicles.},
doi = {10.1021/la052447x},
journal = {Langmuir},
number = ,
volume = 22,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}