Small-angle neutron scattering microemulsions

The structure of microemulsions have been studied by a variety of experimental means. Scattering experiments yield the droplet size or persistence length (3-6 nm) for nonspherical phases. Small-angle neutron scattering (SANS) [123] and x-ray scattering [124] experiments are appropriate however, the isotopic substitution of D2O for H2O... 

K. V. Schubert, R. Strey. Small-angle neutron scattering from microemulsion near the disorder Une in water/formamide-octane-C,E systems. J Chem Phys 95 8532-8545, 1991. 

By small-angle neutron scattering experiments on water/AOT/hydrocarbon microemulsions containing various additives, the change of the radius of the miceUar core with the addition of small quantities of additives has been investigated. The results are consistent with a model in which amphiphilic molecules such as benzyl alcohol and octanol are preferentially adsorbed into the water/surfactant interfacial region, decreasing the micellar radius, whereas toluene remains predominantly in the bulk hydrocarbon phase. The effect of n-alcohols on the stability of microemulsions has also been reported [119],... 

Robinson BH, Toprakcioglu C, Dore JC, Chieux P (1984) Small-Angle Neutron-Scattering Study of Microemulsions Stabilized by Aerosol-Ot.l. Solvent and Concentration Variation. J Chem Soc Faraday Trans 1 80 13-27... 

Water-in-fluorocarbon emulsions, stabilised with fluorinated nonionic surfactants, were investigated by small angle neutron scattering (SANS) spectroscopy [8,99]. The results indicated that the continuous oil phase comprised an inverse micellar solution, or water-in-oil microemulsion, with a water content of 5 to 10%. However, there was no evidence of a liquid crystalline layer at the w/o interface. A subsequent study using small angle x-ray scattering (SAXS) spectroscopy gave similar results [100]. 

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. 

Another interesting technique able to investigate the microstructure of dense microemulsions is represented by the small-angle neutron scattering (SANS) (de Campo et al., 2004). 

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. 

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... 

Eastoe J, Cazelles BMH, Ste5Tler DC, Holmes JD, Pitt AR, Wear TJ, Heenan RK. Water-in-C02 microemulsions studied by small-angle neutron scattering. Langmuir 1997 13 6980-6984. 

Lee CT, Johnston KP, Dai HJ, Cochran HD, Melnichenko YB, Wignall GD. Droplet interactions in water-in-carbon dioxide microemulsions near the critical point a small-angle neutron scattering study. J Phys Chem B 2001 105 3540-3548. 

Chen, S.H. (1986) Small angle neutron scattering studies of the structure and interaction in micellar and microemulsions. Ann. Rev. Phys. Chem., 37, 351-399. 

Schubert, K.-V., Strey, R., Kline, S. and Kaler, E.W. (1994) Small-angle neutron scattering near the Lifshitz lines Transition from weakly structured mixtures to microemulsions. /. Chem. 

Gradzielski, M., Langevin, D., Magid, L. and Strey, R. (1995) Small-angle neutron scattering from diffuse interfaces. 2. Polydisperse shells in water n-alkane-C10E4 microemulsions. /. Phys. Chem., 99, 13232-13238. 

Arleth, L. and Pedersen, J.S. (2001) Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering. Phys. Rev. E, 63, 61406-61423. 

Bagger-Jorgensen, H., Olsson, U. and Mortensen, K. (1997) Microstructure in a ternary microemulsion studied by small angle neutron scattering. Langmuir, 13, 1413-1421. 

Sottmann, T., Strey, R. and Chen, S.-H. (1997) A small-angle neutron scattering study of nonionic surfactant molecules at the water-oil interface Area per molecule, microemulsion domain size, rigidity. /. Chem. Phys., 106, 6483-6491. 

In Ref. [42], PEO was embedded in a w/o-droplet microemulsion and studied by small-angle neutron scattering. The authors state that this polymer does not adsorb considerably at the SDS monolayer. The important statement is that both the size polydispersity and the shape fluctuations are increased compared to the reference system without polymer. Larger shape fluctuations are also found for gelatine embedded in w/o-droplet microemulsions (see Fig. 4.10 in [43]). Here, by strong confinement, the elongated shapes... 

Zielinski, R.G., Kline, S.R., Kaler, E.W. and Rosov, N. (1997) A small-angle neutron scattering study of water in carbon dioxide microemulsions. Langmuir, 13, 3934-3937. 

Rananavare, S.B., Ward, A.J.I., Osborne, D.W., Friberg, S.E. and Kaiser, H. (1988) A small-angle neutron-scattering study of a nonaqueous 3-component microemulsion. /. Phys. Chem., 92, 5181-5183. 

Schubert, K.V. and Strey, R. (1991) Small-angle neutron-scattering from microemulsions near the disorder line in water formamide octane QEj systems. /. Chem. Phys., 95, 8532-8545. 

Co, C.C. and Kaler, E.W. (1998) Particle size and monomer partitioning in microemulsion polymerization 2. Online small angle neutron scattering studies. Macromolecules, 31,3203-3210. 

Harrison et al. reported the first w/c microemulsion in 1994 (20). A hybrid surfactant, namely F7H7, made of respectively one hydrocarbon and one fluorocarbon chain attached onto the same sulfate head group, was able to stabilize a w/c microemulsion at 35 and 262 bar. For a surfactant concentration of 1.9 wt %, water up to a w = 32 value ([water]/surfactant]) could be dispersed. A spherical micellar structure was confirmed by small-angle neutron scattering (SANS) experiments (21). This surfactant was later the subject of dynamic molecular simulations (22, 23). The calculations were consistent with the SANS data and high diffusivity was predicted, highlighting this important feature of low-density and low-viscosity supercritical fluids (SCF). 

Microemulsion structures were investigated by high-pressure small-angle neutron scattering (SANS). Engineering considerations limit the maximum pressure of the SANS cell to about 600 bar. Therefore, the experimental conditions were chosen as T= 15°C and P = 500 bar, so as to strike a compromise between this and the need to minimize attractive interactions, which increase on approach to Pg. The scattering was consistent with the added D2O... 

Eastoe, Julian Gazelles, Beatrice M. H. Steytler, David C. Holmes, Justin D. Pitt, Alan R. Wear, Trevor J. Heenan, Richard K. Water-in-C02 Microemulsions Studied by Small-Angle Neutron Scattering. Langmuir 1997, 13(26), 6980-6984. 

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