Confinement of a hydrophilic polymer in membrane lyotropic phases

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.