Interconnected Networks: Structural and Dynamic Characterization of Aqueous Dispersions of Dioctanoylphosphatidylcholine

Nostro, Pierandrea Lo; Murgia, Sergio; Lagi, Marco; Fratini, Emiliano; Karlsson, Göran; Almgren, Mats; Monduzzi, Maura; Ninham, Barry W.; Baglioni, Piero

doi:10.1021/jp803983t

Cited by 14 publications

(13 citation statements)

References 58 publications

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“…short chain phospholipids like dioctanoylphosphatidylcholine, diC 8 PC) exhibit an upper consolute (cloud) point in their temperature vs. concentration phase diagram [57][58][59]. On the other hand non ionic surfactacts such as C i E j exhibit a lower consolute cloud point [60].…”

Section: Remark On Ionic Surfactants and Cloud Points Compatibility mentioning

confidence: 99%

Two sides of the coin. Part 1. Lipid and surfactant self-assembly revisited

Ninham

Larsson

Nostro

2017

Colloids and Surfaces B: Biointerfaces

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a b s t r a c tHofmeister, specific ion effects, hydration and van der Waals forces at and between interfaces are factors that determine curvature and microstructure in self assembled aggregates of surfactants and lipids; and in microemulsions. Lipid and surfactant head group interactions and between aggregates vary enormously and are highly specific. They act on the hydrophilic side of a bilayer, micelle or other self assembled aggregate. It is only over the last three decades that the origin of Hofmeister effects has become generally understood. Knowledge of their systematics now provides much flexibility in designing nanostructured fluids.The other side of the coin involves equally specific forces. These (opposing) forces work on the hydrophobic side of amphiphilic interfaces. They are due to the interaction of hydrocarbons and other "oils" with hydrophobic tails of surfactants and lipids. The specificity of oleophilic solutes in microemulsions and lipid membranes provides a counterpoint to Hofmeister effects and hydration. Together with global packing constraints these effects determine microstructure.Another factor that has hardly been recognised is the role of dissolved gas. This introduces further, qualitative changes in forces that prescribe microstructure.The systematics of these effects and their interplay are elucidated. Awareness of these competing factors facilitates formulation of self assembled nanostructured fluids. New and predictable geometries that emerge naturally provide insights into a variety of biological phenomena like anaesthetic and pheromone action and transmission of the nervous impulse (see Part 2).

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Section: Remark On Ionic Surfactants and Cloud Points Compatibility mentioning

confidence: 99%

Two sides of the coin. Part 1. Lipid and surfactant self-assembly revisited

Ninham

Larsson

Nostro

2017

Colloids and Surfaces B: Biointerfaces

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“…2 Specifically, it has been investigated both experimentally 3 and theoretically 4 that deviations (defects) from the predominant cylindrical shape such as spherical end-caps and branched junction points do influence the rheological behaviour of these complex solutions. The interplay between branched networks and linear wormlike micelles was the subject of several studies for aqueous solutions of non-ionic surfactants, [5][6][7][8] whereas the oil continuous counterpart solutions have received less attention. A few exceptions include studies on wormlike reverse micelles formulated, e.g., with sucrose-based lipophilic nonionic surfactants 9 and with the zwitterionic biocompatible surfactant lecithin (phosphatidyl-choline), which is able to form both branched and unbranched wormlike reverse micelles depending on the nature of the organic solvent used as the continuous phase.…”

Section: Introductionmentioning

confidence: 99%

Impact of branching on the viscoelasticity of wormlike reverse micelles

et al. 2012

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We present an investigation on the effect of inter-micellar connections (branches) on the rheology of wormlike micelles. The system chosen is made of lecithin, minute amounts of water and organic solvents. Lecithin and water self-assemble into wormlike reverse micelles that can be branched or unbranched depending on the oil composition (and on the water content). In this respect, cyclohexane favours disconnected reverse micelles while isooctane promotes the formation of branches. By using mixtures of cyclohexane and isooctane as the oil phase and different water/lecithin ratios, the branch density of the system can be finely tuned. PGSE-NMR experiments allowed us to distinguish between branch-free (unbranched) and branched systems and the response of the very same samples to mechanical stress was measured by rheology. This allows, for the first time, an experimental correlation between rheological properties and the presence of branches. It turned out that the presence of a few inter-micellar connections sensibly decreases the zero-shear viscosity measured in steady state flow curves. Comparison with oscillatory rheology experiments indicates that the main effect of branches is to shorten the terminal relaxation time by speeding-up the reptation

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“…Often, a minimum in surfactant diffusion and a maximum in viscosity are the signature of the presence of cylindrical wormlike micelles [23]. These critical points highlight the transition from the dilute (micelles are individual entities) to the semi-dilute (micelles start to entangle/interconnect) regime that brings to a huge increase in the viscosity while the lateral diffusion of the surfactant is associated with an increase in the observed self-diffusion coefficient.…”

Section: Surfactant Diffusionmentioning

confidence: 99%