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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}
}
  • Mixtures of cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzene sulfonate (SDBS) in water form a fluid lamellar phase at {le}40 wt % water but surprisingly turn into viscous gels at higher water fractions. The gels are characterized by spherulite and other bilayer defects consistent with a low bending elasticity, {kappa} {approx} k{sub B}T, and a nonzero spontaneous curvature. Caill{acute e} analysis of the small-angle x-ray line shape confirms that for 7:3 wt:wt CTAT:SDBS bilayers at 50% water, {kappa} = 0.62 {+-} 0.09 k{sub B}T and {kappa} = -0.9 {+-} 0.2 k{sub B}T. For 13:7 wt:wt CTAT:SDBS bilayers, the measured bending elasticitymore » decreases with increasing water dilution in good agreement with predictions based on renormalization theory, giving {kappa}{sub 0} = 0.28 k{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 formed at even higher water fractions to be equilibrium structures.« less
  • Surfactant vesicles containing monomers in the interior of the bilayer were used to template hollow polymer nanocapsules. This study investigated the formation of surfactant/monomer assemblies by two loading methods, concurrent loading and diffusion loading. The assembly process and the resulting aggregates were investigated with dynamic light scattering, small angle neutron scattering, and small-angle X-ray scattering. Acrylic monomers formed vesicles with a mixture of cationic and anionic surfactants in a broad range of surfactant ratios. Regions with predominant formation of vesicles were broader for compositions containing acrylic monomers compared with blank surfactants. This observation supports the stabilization of the vesicular structuremore » by acrylic monomers. Diffusion loading produced monomer-loaded vesicles unless vesicles were composed from surfactants at the ratios close to the boundary of a vesicular phase region on a phase diagram. Both concurrent-loaded and diffusion-loaded surfactant/monomer vesicles produced hollow polymer nanocapsules upon the polymerization of monomers in the bilayer followed by removal of surfactant scaffolds.« less
  • In this work, the phase equilibria of binary amphiphilic-water systems are studied, where the amphiphilic molecule is composed of a cationic (A ) and an anionic (A surfactant in equimolar ratio, and the inorganic counterions are eliminated (catanionic surfactant). The catanionic compounds studied are dodecylammonium dodecanoate, dodecylammonium dodecyl sulfate, dodecyltrimethylammonium dodecyl sulfate, and dodecylethyldimethylammonium dodecyl sulfate. As all the ionic surfactants have approximately the same solubility in water, the electrostatic effects in the system can be neglected. Below 373 K, the catanionic surfactant-water systems show similar phase behavior as lecithin-water systems, where a lamellar phase is in equilibrium with almostmore » pure water. In both cases, the swelling of the lamellae is assumed to be due to the hydration force interactions between the bilayers. However, due to the structure of the polar headgroup, the catanionic systems are easier to describe in theoretical model studies of hydration force than the zwitterionic phospholipid systems. The experimental results show that the strength of the hydration force is more dependent on the size of the polar headgroups than the specific chemical composition of them. Furthermore, no hydrophobic attraction could be observed between the bilayers. The results are also discussed in light of some main theories that are suggested for the repulsive hydration force and the attractive hydrophobic interaction.« less