Measurement of the Membrane Flexibility in Lamellar and “Sponge” Phases of the C12E5/Hexanol/Water System

Abstract

The present work is primarily concerned with the measurement, by several different methods (using X-ray and static light scattering experiments or dynamic light scattering experiments), of the elasticity of bilayers made up of n-dodecyl pentaethylene glycol monoether (C12E5) and hexanol molecules. The membrane bending elasticity modulus, κ, has been measured for both the Lα (lamellar) and the L3 (“sponge”) phase of the C12E5/hexanol/water system. For the lamellar phase, κ was measured using both the excess area and the dynamics of the fluctuations, while for the sponge phase κ was measured using only the excess area. The values of κ measured seem to be of the same order (approximately kBT) for both the lamellar phase and the sponge phase, although the molar ratio of hexanol to C12E5 is 4 times bigger in the sponge phase. The effect of temperature on κ was also studied: the slight increase in κ found for this system with temperature seems to be related to a decreasing polar head area of the C12E5 molecule...