Flexible bilayers with spontaneous curvature lead to lamellar gels and spontaneous vesicles

Bret A. Coldren, Heidi Warriner, Ryan Van Zanten, Joseph A. Zasadzinski, Eric B. Sirota

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Mixtures of cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzene sulfonate (SDBS) in water form a fluid lamellar phase at ≤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, κ ∼ kBT, and a nonzero spontaneous curvature. Caillé analysis of the small-angle x-ray line shape confirms that for 7:3 wt:wt CTAT=SDBS bilayers at 50% water, κ = 0.62 ± 0.09 kBT and κ = -0.9 ± 0.2 k BT. 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 κo = 0.28 kBT. These results show that surfactant mixing is sufficient to make κ ∼ kBT, 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.

Original languageEnglish (US)
Pages (from-to)2524-2529
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number8
DOIs
StatePublished - Feb 21 2006

Keywords

  • Bending constants
  • Electron microscopy
  • Phase behavior
  • X-ray scattering

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