Percolation in Nonionic Water-in-Oil−Microemulsion Systems:  A Small Angle Neutron Scattering Study

Lipgens, S.; Schübel, Dirk; Schlicht, L.; Spilgies, Jan-Hendrik; Ilgenfritz, G.; Eastoe, Julian; Heenan, Richard K.

doi:10.1021/la9701790

Cited by 49 publications

(68 citation statements)

References 45 publications

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“…Similarly, in ME composed of disconnected cylinders, the length distribution is determined by the balance between the curvature energy required to form the end-caps of the cylinders, 1 , and their translational entropy. Moreover, we show that the connectivity transition when the network is formed from disconnected cylinders takes place when the junction and the end-cap energies are comparable, 3 1 [11]. All this makes an accurate estimate of the curvature energies of these two types of topological defects a crucial ingredient of our theory, essential for understanding the relation between structure and thermodynamics and for comparison with experiment.…”

Section: Introductionmentioning

confidence: 79%

“…High-genus junctions are also unfavourable due to the saddles introduced by their shape (topologically, each junction corresponds to z/2 − 1 handles). For the connected network (z = 3) the exponent ( 3 2 ) governing the dependence of the free energy on the volume fraction is higher than linear, resulting in an effective attraction. When the network is broken into free cylinders (z = 1), the ideal gas of junctions is replaced by an ideal gas of end-caps, of number density ρ 1 , that each cost curvature energy 1 .…”

Section: Network Free Energy and Phase Behaviourmentioning

confidence: 99%

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Microemulsion networks: the onset of bicontinuity

Tlusty

Safran

2000

J. Phys.: Condens. Matter

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We predict theoretically the gradual formation of fluctuating, connected microemulsion networks from disconnected cylinders as the spontaneous curvature and the radius are varied, in agreement with recent direct measurements of these topological transitions. We discuss the role of the topological defects, the network junction and the end-cap of the disconnected cylinders, in the connectivity transition. The optimal shapes and curvature energies of the junctions and end-caps are calculated numerically and compared with analytic approximations.

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Section: Introductionmentioning

confidence: 79%

Section: Network Free Energy and Phase Behaviourmentioning

confidence: 99%

Microemulsion networks: the onset of bicontinuity

Tlusty

Safran

2000

J. Phys.: Condens. Matter

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“…1. Igepal, like AOT, forms well-characterized, monodispersed, spherical reverse micelles (33). Igepal is a nonionic surfactant with a head group terminated by an alcohol hydroxyl.…”

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confidence: 99%

“…The equivalent analysis is not possible for the Igepal reverse micelles. The sizes of smaller Igepal reverse micelles (under Ϸw 0 ϭ 10) are not well-characterized, so it is not possible to have a well-defined small reverse micelle to use as a model for the interfacial water spectrum (33). The Igepal surfactant has hydroxyl head groups that will exchange deuterium atoms with the HOD molecules in the water nanopool.…”

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confidence: 99%

Water dynamics at neutral and ionic interfaces

Fenn

Wong

Fayer

2009

Proc. Natl. Acad. Sci. U.S.A.

140

194

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The orientational dynamics of water at a neutral surfactant reverse micelle interface are measured with ultrafast infrared spectroscopy of the hydroxyl stretch, and the results are compared to orientational relaxation of water interacting with an ionic interface. The comparison provides insights into the influence of a neutral vs. ionic interface on hydrogen bond dynamics. Measurements are made and analyzed for large nonionic surfactant Igepal CO-520re-verse micelles (water nanopool with a 9-nm diameter). The results are compared with those from a previous study of reverse micelles of the same size formed with the ionic surfactant Aerosol-OT (AOT). The results demonstrate that the orientational relaxation times for interfacial water molecules in the two types of reverse micelles are very similar (13 ps for Igepal and 18 ps for AOT) and are significantly slower than that of bulk water (2.6 ps). The comparison of water orientational relaxation at neutral and ionic interfaces shows that the presence of an interface plays the dominant role in determining the hydrogen bond dynamics, whereas the chemical nature of the interface plays a secondary role.reverse micelles ͉ ultrafast IR experiments ͉ interfacial water ͉ hydrogen bond dynamics W ater molecules at interfaces are involved in many processes. In biology, water is found in crowded environments, such as cells, where it hydrates membranes and large biomolecules. In geology, interfacial water molecules can control ion adsorption and mineral dissolution. Embedded water molecules can change the structure of zeolites. In chemistry, water plays an important role as a polar solvent often in contact with interfaces, for example, in ion exchange resin systems.When water interacts with an interface, its hydrogen bonding properties are distinct from those of bulk water. Interactions with an interface influence water's ability to undergo hydrogen bond network rearrangements, which is a concerted process that involves a water molecule and its two water solvation shells (1, 2). For a water molecule to switch hydrogen bonding partners, other waters must also break and form new hydrogen bonds (1, 2). Such hydrogen bond rearrangements are necessary for both orientational and translational motions. An interface eliminates many of the pathways for hydrogen bond rearrangement that are available in bulk water. A fundamental question is whether the composition of or solely the presence of an interface plays the dominant role in affecting the hydrogen bond dynamics of interfacial water.Ultrafast infrared (IR) spectroscopy is a valuable technique for probing the dynamics of both bulk water and water at interfaces using the hydroxyl stretching mode of water as a reporter (3-17). Because processes in water involving hydrogen bond rearrangements occur on the picosecond time scale, the femtosecond time resolution of the IR techniques makes it possible to resolve the motions of water molecules on the time scale on which they are occurring. Examples of confined or restricted environments that...

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“…The Igepal structure is shown in FIGURE 2C. Igepal forms monodispersed, spherical reverse micelles (14). Igepal w 0 ϭ 20 reverse micelles have the same size water nanopool, i.e., a diameter of 9 nm, as w 0 ϭ 25 AOT reverse micelles.…”

Section: How Much Does a Charged Vs Uncharged Interface Matter?mentioning

confidence: 99%

Water in a Crowd

Fayer

2011

Physiology

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In many situations, form biology to geology, water occurs not as the pure bulk liquid but rather in nanoscopic environments, in contact with interfaces, interacting with ionic species, and interacting with large organic molecules. In such situations, water does not behave in the same manner as it does in the pure bulk liquid. Water dynamics are fundamental to many processes such as protein folding and proton transport. Such processes depend on the dynamics of water's hydrogen bonding network. Here, the results of ultrafast infrared experiments are described that shed light on the influences of nanoconfinement, interfaces, ions, and organic molecules on water hydrogen bond dynamics.

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Percolation in Nonionic Water-in-Oil−Microemulsion Systems: A Small Angle Neutron Scattering Study

Cited by 49 publications

References 45 publications

Microemulsion networks: the onset of bicontinuity

Microemulsion networks: the onset of bicontinuity

Water dynamics at neutral and ionic interfaces

Water in a Crowd

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