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1170 Langmuir 1992,8, 1170-1175 Membrane Curvature Elasticity in Weakly Charged

Summary: 1170 Langmuir 1992,8, 1170-1175
Membrane Curvature Elasticity in Weakly Charged
Lamellar Phases
J. L. Harden,',' C. Marques, and J.-F. Joanny
Institut Charles Sadron, 6 rue Boussingault, 67083 Strasboi, >.gCedex, France
D. Andelman
School of Physics and Astronomy, Tel-Aviv University, Ramat-Aviv 69978, Tel-Aviv, Israel
Received September 30, 1991. I n Final Form: January 23, 1992
We study the effect of electrostatic interactions on the membrane bending energiesof weaklycharged,
swollen,lamellar phases of surfactant solutions. We treat the surface charge density of the lamellae as
a constant and consider only situations where it is low enough so that the distance 2d between lamellae
is the smallest relevant length scale in the problem. In the presence of salt (the short-distance Debye-
Huckel regime) we show that the electrostatic contribution to the bending energy of a membrane is in
general small, in disagreement with a previous result, is proportional to d3,and is independent of ionic
strength. Identical results areobtained formembranes undulating sinusoidallyinphaseand forconcentric
cylindrical membranes. The bending constant is alsocalculated for membranes held at constant electric
potential and iscomparedtotheconstant chargedensitycase. Inthe absenceof salt,continuity arguments
predictanelectrostaticcontribution tothebendingenergythatscalesasd3. Furthermore,adirectcalculation
for concentric cylindrical membranes gives exactly the same scaling behavior (including the numerical
prefactor) as in the presence of salt.


Source: Andelman, David - School of Physics and Astronomy, Tel Aviv University


Collections: Materials Science; Physics