RESUMEN
We study the confinement of a hydrophilic polymer (polyethylene glycol or PEG) between the bilayers of the zwitterionic surfactant tetradecyldimethyl aminoxide (C(14)DMAO). Small angle X-ray scattering and electron microscopy experiments show that the polymer modifies the physical properties of the lyotropic smectic (L(alpha)) phase. The observed effects are similar to those reported for anchored hydrophobically-modified polymers, indicating a strong interaction between PEG and the C(14)DMAO bilayers. Self-diffusion experiments performed in the lyotropic sponge (L(3)) phase show that the polymer adsorbs onto the surfactant membranes. This adsorption explains earlier observations: high polymer concentrations decrease the Gaussian rigidity of the membranes and a vesicular phase is stabilized.
RESUMEN
We study the sponge phase of the mixed non-ionic/ionic surfactant system C14DMAO-TTAB-hexanol-brine. Our aim is to determine if this phase exists in this mixed system and if it preserves or changes its structure when the relative amount of the charged surfactant is increased in the mixture. SAXS, FFEM, and conductivity results show that for the same bilayer volume fraction the sponge phase preserves its global structure. We propose a method to determine the geometrical obstruction factor from electrical conductivity measurements in ionic sponge phases. Analysis of lamellar phases in the same system shows that the bilayer thickness increases when the ionic surfactant concentration is increased.