[Show abstract][Hide abstract] ABSTRACT: The ability to induce morphological transitions in water-in-oil (w/o) and water-in-CO2 (w/c) microemulsions stabilized by a tri-chain anionic surfactant 1,4-bis(neopentyloxy)-3-(neo-pentyloxycarbonyl)-1,4-dioxobutane-2-sulfonate (TC14) with simple hydrotrope additives has been investigated. High pressure small-angle neutron scattering (SANS) has revealed the addition of a small mole fraction of hydrotrope can yield a significant elongation in the microemulsion water droplets. For w/o systems, the degree of droplet growth was shown to be dependent on the water content, the hydrotrope mole fraction and chemical structure; whereas for w/c microemulsions a similar, but less significant effect was seen. The expected CO2 viscosity increase from such systems has been calculated and compared to related literature using fluorocarbon chain surfactants. This represents the first report of hydrotrope induced morphology changes in w/c microemulsions, and is a significant step forward towards the formation of hydrocarbon worm-like micellar assemblies in this industrially relevant solvent.
[Show abstract][Hide abstract] ABSTRACT: Since the discovery of microemulsions by Jack H. Shulman, there have been huge progresses made in applying microemulsion syst ems in a plethora of research and industrial processes. Microemulsions are clear, stable, isotropic mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. Microemulsions are optically isotropic and thermodynamically stable liquid solutions of oil, water and amphiphile. To date microemulsions have been shown to be able to protect labile drug, control drug release, increase drug solubility, increase bioavailability and reduce patient variability. Furthermore, it has proven possible to formulate preparations suitable for most routes of administration. Since the discovery of microemulsions, they have attained increasing significance both in basic research and in industry. Due to their unique proper ties, namely, ultralow interfacial tension, large interfacial area, thermodynamic stability and the ability to solubilise otherwise immiscible liquids, uses and applications of microemulsions have been numerous. Microemulsions are readily distinguished from normal emulsions by their transparency, low viscosity and more fundamentally their thermodynamic stability. Microemulsions are shown to be effective dermal delivery mechanism for several active ingredients for pharmaceutical and cosmetic applications. Topical microemulsions allow rapid penetration of active molecules due to the large surface area of the internal phase, and their components reduce the barrier property of stratum corneum. Microemulsions thereby enhance dermal absorption compared with conventional formulations and are therefore a promising vehicle due to their pot ential for transdermal drug delivery.
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