A new approach to lamellar phases (L_α) in water – non-ionic surfactant systems

Lyotropic Lamellar Polysiloxanes with Isomeric Amphiphilic Side Chains

“…The low concentration part of the phase diagram of nonionic surfactants, which show an intersection of the L a phase and the upper miscibility gap (as observed for P1), is rather complicated -a schematic phase diagram can be found in ref. [19] -and may be even more complex for aqueous polymer solutions which, due to polydispersity, are not genuine binary systems.…”

Disconnected lamellar phases in pseudobinary water–non-ionic surfactant systems: A general phenomenon

“…In our previous study [8] we demonstrated that the highly diluted and the disconnected L α phase are not two different phenomena but that they belong together. In this study the development of a continuous L α phase extending to low concentrations (C 10 E 4 ) into an L α phase restricted to high concentrations (C 10 E 5 ) was investigated.…”

“…Mixtures of C 12 E 5 /C 12 E 6 were chosen as, according to [8], the disconnection can be tuned simply by mixing two surfactants, one of which forms a continuous L α phase extending down to low concentrations (C 12 E 5 ), whereas the other L α phase is restricted to high concentrations (C 12 E 6 ). The phase diagrams were monitored by visual observation, the type of the lyotropic liquid crystals was determined via polarization microscopy, and the structural development was followed with small angle X-ray scattering (SAXS) along specific paths through the phase diagrams.…”

“…This was a surprise since C 12 E 5 is a non-ionic surfactant, i.e., that stabilizing electrostatic forces are lacking, and a formation of a structured phase at surfactant concentrations as low as 1 wt% was not expected. Indeed, dilute lamellar phases in binary waternon-ionic surfactant systems turned out to be a special feature of a small numbers of surfactants only, namely C 12 E 5 [6], C 12 E 4 [7], C 10 E 4 [8], C 10 E 3 [9], and three surfactants, the hydrophobic parts of which are branched [10,11]. The influence of the molecular structure on the absence or presence of the dilute L α phase can be demonstrated very well with the phase diagrams of binary water-C 12 E j systems.…”

Effect of cholesterol on diffusion in surfactant bilayers

“…The molecular order of the lamellar phase is maintained by van der Waals forces between the alkyl chains and hydrogen bonding forces between water molecules and the lipid headgroups. 7 During the FCS measurements, we probe the bilayer dynamics in a volume of Ϸ0.5 m 3 , at a distance of 60 m from the cover glass surface. Because this distance leaves room for about 7000-9000 bilayers, we may assume that surface effects are no longer important and the bilayers are randomly oriented.…”