Microemulsions freeze fracture electron

M. A. Bolzinger-Thevenin, I. L. Grossiord, and M. C. Poelman, Characterization of a sucrose ester microemulsion by freeze fracture electron micrograph and small angle neutron scattering experiments, Langmuir, 15 (1999) 2307-2315. 

Jahn, W., and Strey, R. (1988), Microstructure of microemulsions by freeze fracture electron microscopy,/. Phys. Chem., 92,2294-2301. 

Figure 1.19 Micrographs of microemulsion droplets of the o/w-type in the system II2O- n-octane-CnEs prepared near the emulsification failure boundary at ya = 0.022, wb = 0.040 and T = 26.1 °C. (a) Freeze-fracture direct imaging (FFDI) picture showing dark spherical oil droplets of a mean diameter = 24 9 nm in front of a grey aqueous background. Note that each oil droplet contains a bright domain of elliptic shape which is interpreted as voids, (b) The freeze-fracture electron microscopy (FFEM) picture supports the FFDI result. Each fracture across droplets which contain bubbles shows a rough fractured surface. (From Ref. [26], reprinted with permission of Elsevier.)...

Burauer, S., Belkoura, L., Stubenrauch, C. and Strey, R. (2003) Bicontinuous microemulsions revisited A new approach to freeze fracture electron microscopy (FFEM). Colloids Surf. A, 159-170. 

Freeze-fracture electron microscopic studies into microstructure have been carried out on several microemulsion systems. Some of the more extensively conducted studies on microemulsion systems are reviewed below. 

J. C. Hatfield, Freeze-fracture electron microscopy and electrical conductivity of microemulsions. Doctoral Dissertation, University of Minnesota, 1978. 

Using various physicochemical techniques such as high resolution NMR, viscosity, and electrical resistivity measurements, Chan and Shah [26] proposed that the middle-phase microemulsion in three-phase systems at or near optimal salinity is a water-external microemulsion of spherical droplets of oil. Extended studies to characterize the middle-phase microemulsions by several techniques including freeze-fracture electron microscopy revealed the structure to be a water-external microemulsion [26]. The droplet size in the middle-phase microemulsion decreases with increasing salinity. A freeze-fracture electron micrograph of a middle-phase microemulsion is shown in Fig. 8. It clearly indicates that the discrete spherical structure of the oil droplets in a continuous aqueous phase is consistent with the mechanism proposed in Fig. 7. This system was extensively studied by Reed and coworkers [20-22]. 

Freeze fracture Electron micrograph of bicontinuous microemulsion... 

X-ray scattering (SAXS), DLS, freeze-fracture electron microscopy (FFEM), or ultraviolet-visible (UV-Vis) spectroscopy. An example of application of [C mim] [PFg]-based microemulsions is areactionmediasynthesisofpoly(methylmethacrylate) [37,38],... 

The size, shape, formation mechanism, and interior polarity of the different IL microemulsions have been studied extensively by various techniques, such as freeze-fracture electron microscopy (FFEM), dynamic light scattering (DLS), conductivity study, UV-Vis spectroscopy with various probe molecules, and SANS study [30-33]. 

For the case of droplet microemulsions, tq = ri = r2, and so the mean curvature H = 1/ro. According to convention, H is positive for oil-in-water (o/w) droplets, and negative for water-in-oil (w/o) droplets. For bicontinuous microemulsions, which according to freeze-fracture electron microscopy have saddle-shaped surfaces of negative and positive curvature (13), c —C2, and so the mean curvature // 0. Note that lamellar liquid crystalline phases (Lc,), which are planar layers of oil and water, also have zero mean curvature (c = c 2 = 0), and are often located at higher surfactant concentrations nearby bicontinuous microemulsion phases (19). 

Figure 1.7 Freeze-fracture electron micrographs showing the structure of the microemulsion phase in the system water/n-octane/Ci2E5. Top microemulsion with a droplet structure that shows the random distribution of the droplets and their small poly-dispersity. Bottom bicontinuous microemulsion that displays the saddle-shaped structures of the film separating oil domains (grained aspect) from water domains (smooth aspect). Reproduced from reference 47 with permission of Springer Verlag.

Strey WJR (1988) Microstructure of microemulsions by freeze fracture electron microscopy. 

Fig, XIV-12. Freeze-fracture transmission electron micrographs of a bicontinuous microemulsion consisting of 37.2% n-octane, 55.8% water, and the surfactant pentaethy-lene glycol dodecyl ether. In both cases 1 cm 2000 A (for purposes of microscopy, a system producing relatively coarse structures has been chosen), [(a) Courtesy of P. K. Vinson, W. G. Miller, L. E. Scriven, and H. T. Davis—see Ref. 110 (b) courtesy of R. Strey—see Ref. 111.]... 

Figure 11. Freeze-fracture transmission electron micrograph of the microemulsion...

Molybdenum sulfide nanoparticles in the size-range 3-10 nm have been synthesized in mild conditions using a microemulsion-based route. The reverse microemulsion phase, AOT/ n-heptane/ water, was first characterized by Transmission Electron Microscopy (TEM) of Freeze Fractures (FF) obtained via High Pressure Freezing (HPF) as well as Dynamic Light Scattering (DLS). The impacts of various parameters such as water-to-surfactant molar ratio w and the addition of a nonionic cosurfactant were then studied. The reverse microemulsion phase was further used to tailor the size of MoSx nanoparticles. The mean particle size obtained by this method makes those particles particularly interesting for further catalytic applications. 

Figure 2.8 Freeze-fracture scanning electron microscopy image from a bicontinuous microemulsion. The system was prepared with the technical surfactant Marlowet IHF and perchloroethylen as oil. (From Ref. [69], unpublished work.)...

Characterization of Microemulsions Using Fast Freeze-Fracture and Cryo-Electron Microscopy... 

Figure 8 Freeze-fracture scanning electron micrograph of a middle-phase microemulsion. The spherical shapes are oil droplets suspended within the continuous aqueous phase. (The black bar represents 0.5 m.)...

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