J. Phys. II France
Volume 2, Numéro 7, July 1992
Page(s) 1439 - 1451
DOI: 10.1051/jp2:1992211
J. Phys. II France 2 (1992) 1439-1451

Vesicles and onion phases in dilute surfactant solutions

B. D. Simons and M. E. Cates

Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, G.B.

(Received 25 February 1992, accepted 8 April 1992)

We study theoretically the stability of phases of unilamellar and multilamellar vesicles in bilayer-forming surfactant solutions. It is argued that these are likely to arise, instead of a bicontinuous "sponge" phase, when the elastic constants of the bilayer are chosen so that the curvature energy of a sphere is small. At very low volume fractions we predict a phase of noninteracting vesicles; as the concentration is increased these reach an overlap threshold, beyond which "nesting" can occur, giving a multilamellar vesicle or "onion" phase. At higher concentration still, a transition to the smectic (L $_{\alpha}$) phase is predicted. This transition may be rather weak if the mean curvature rigidity is small. The relevance of our results to recent experimental work is briefly discussed.

64.70J - 64.70M - 82.60L

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