Light scattering microemulsions

By dynamic light scattering it was found that, in surfactant stabilized dispersions of nonaqueous polar solvents (glycerol, ethylene glycol, formamide) in iso-octane, the interactions between reversed micelles are more attractive than the ones observed in w/o microemulsions, Evidence of intermicellar clusters was obtained in all of these systems [262], Attractive intermicellar interactions become larger by increasing the urea concentration in water/AOT/ -hexane microemulsions at/ = 10 [263],... 

Small-angle neutron scattering (SANS) can be applied to food systems to obtain information on intra- and inter-particle structure, on a length scale of typically 10-1000 A. The systems studied are usually disordered, and so only a limited number of parameters can be determined. Some model systems (e.g., certain microemulsions) are characterized by only a limited number of parameters, and so SANS can describe them fully without complementary techniques. Food systems, however, are often disordered, polydisperse and complex. For these systems, SANS is rarely used alone. Instead, it is used to study systems that have already been well characterized by other methods, viz., light scattering, electron microscopy, NMR, fluorescence, etc. SANS data can then be used to test alternative models, or to derive quantitative parameters for an existing qualitative model. 

Although NMR results provide perhaps the most convincing evidence of the bicontinuous structure of some microemulsions, many other techniques support their existence. These techniques include electrical conductimetry, x-ray and neutron scattering, quasielastic light scattering, and electron... 

Shioi, A., Harada, M., and Tanabe, M. (1995), Static light scattering from oil-rich microemulsions containing polydispersed cylindrical aggregates in sodium bis(2-ethylhexyl) phosphate system,/. Phys. Chem., 99,4750 1756. 

C. Micellar and microemulsion shell thickness determination by combination of light scattering and neutron scattering... 

Sjoblom, E. Friberg, S.E. Light Scattering and Electron Microscopy Determinations of Association Structures in W/0 Microemulsions Journal of Colloid and Interface Sci 1978, Vol. 67, No. 1. 

Table 5. Diffusion Coefficients Measured by Dynamic Light Scattering of AOT/Water Droplets in Various Alkane/AOT/Water Microemulsions as a Function of Pressure. T= 25°C, W= 5, Faot 0.015 mole fraction.

Shukla, A. Kiselev, M.A. Hoell, A. Neubert, R.H.H. Characterization of nanoparticles of lidocaine in w/o microemulsions using small-angle neutron scattering and dynamic light scattering. Pramana-Journal of Physics... 

Baker, R.C. Florence, A.T. Ottewill, R.H. Tadros, T.F. Investigations into the formation and characterisation of microemulsions 2. Light scattering, conductivity and viscosity studies of microemulsions. J. Colloid Interf. Sci. 1984, 100, 332-349. 

Structure of Reverse Micelle and Microemulsion Phases in Near-Critical and Supercritical Fluid as Determined from Dynamic Light-Scattering Studies... 

Dynamic light scattering methods were used to study reverse micelle and microemulsion phases formed in liquid and supercritical alkane continuous phases. 

In this paper we use dynamic light scattering (DLS) methods to examine micelle size and clustering in (1) supercritical xenon, (2) near-critical and supercritical ethane, (3) near-critical propane as well as (4) the larger liquid alkanes. Reverse micelle or microemulsion phases formed in a continuous phase of nonatomic molecules (xenon) are particularly significant from a fundamental viewpoint since both theoretical and certain spectroscopic studies of such systems should be more readily tractable. Diffusion coefficients obtained by DLS for AOT microemulsions for alkanes from ethane up to decane are presented and discussed. It is shown that micelle phases exist in equilibrium with an aqueous-rich liquid phase, and that the apparent hydrodynamic size, in such systems is highly pressure dependent. 

Figure 1. Apparatus for high-pressure dynamic light scattering of microemulsions.

The behavior of water in oil microemulsions has been studied using different techniques light scattering, electrical conductivity, viscosity, transient electrical birefringence, ultrasonic absorption. All these experiments lead us to propose a picture of the microemulsions structure which assignes an important role to the fluidity of the interfacial region. 

It was proved by scattering studies (1-9) that water in oil microemulsions at low water content are dispersions of identical spherical droplets in a continuous oil phase. Dilution procedure and light scattering measurements (both the intensity and the correlation function of the scattered light) allow to measure the osmotic compressibility and the diffusion coefficient of the droplets ... 

The Kerr constant around cf> v0.1 becomes very large for ATB microemulsions and the decay curve becomes exponential.The measured decay time t is in fairly good agreement with the lifetime tg of a critical density fluctuation of size . is the correlation length of the density fluctuations previously measured in ATB microemulsion by light scattering and 3... 

Several structural studies have shown that in the oil rich part of the phase diagram, microemulsions consist of a dispersion of mono-disperse water droplets in interaction (7-8). In recent papers (9-10), we have investigated by light scattering the effect of the micellar... 

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