Investigation of W/O microemulsion droplets by contrast variation light scattering |
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Authors: | Anuj Shukla Reinhard H H Neubert |
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Institution: | 1. Department of Pharmacy, Institute of Pharmaceutics and Biopharmaceutics, Martin-Luther-University Halle-Wittenberg, D-06120, Halle/Saale, Germany
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Abstract: | Dynamic and static light scattering experiments have been performed at various molar ratios (γ) of water to AOT and temperatures
on water-in-oil (W/O) microemulsions dispersed in n-heptane, n-octane, and n-nonane. Size and shape fluctuations of microemulsion
droplets are determined with very high precision because polydispersity influences the characteristic features of scattering
data as well as the hydrodynamic radius withγ. Self-consistent interpretation of dynamic and static light scattering data using optical properties and packing consideration
on the basis of the layered sphere model are obtained. The estimated extent of polydispersity index of 17% is found, whereas
the polydispersity is independent of the alkane types. The geometrical parameters, e.g., hydrodynamic radius, area per head
group of the surfactant molecule and thickness of the surfactant layer of microemulsion droplets are also estimated and compared
in three different n-alkane types. The best interpretation of the temperature dependence of data has shown a transition from
spherical droplets to ellipsoid aggregates with increasing temperature. Axial ratio increases with increase of temperature
and the longer the alkane the larger is the axial ratio. The parameters describing the polydispersity and shape change are
in agreement with theoretical and experimental results found in the literature |
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Keywords: | Microemulsions static and dynamic light scattering |
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